Camera having networked printer

ABSTRACT

A camera for capturing and printing images is provided having an image sensor for capturing images, a network interface for transferring the captured images to a computer system and for receiving identities uniquely assigned to each transferred image by the computer system, and a printing mechanism for printing the images and coded data at least partially indicative of the assigned identities onto print media.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a Continuation of U.S. application Ser. No.10/986,375 filed on Nov. 12, 2004, which is a Continuation of U.S.application Ser. No. 09/608,920 filed on Jun. 30, 2000, now issued U.S.Pat. No. 6,831,682, all of which are herein incorporated by reference.

FIELD OF INVENTION

The present invention relates to a digital camera with an integralprinter for printing an interface onto an surface to produce aninterface surface, and, in particular, for printing photos asinterfaces.

The invention has been developed primarily to produce interface surfaceswhich allow users to interact with networked information and to obtaininteractive printed matter on demand via high-speed networked colorprinters. Although the invention will largely be described herein withreference to this use, it will be appreciated that the invention is notlimited to use in this field.

CO-PENDING APPLICATIONS

Various methods, systems and apparatus relating to the present inventionare disclosed in the following co-pending applications/granted patentsfiled by the applicant or assignee of the Present invention on Jun. 30,2000:

6,238,044 6,425,661 6,471,331 6,676,250 6,347,864 6,439,704 6,425,7006,588,952 6,824,044 6,678,499 6,976,220 6,976,035 6,766,942 7,286,1136,922,779 6,978,019 7,406,445 6,959,298 6,973,450 7,150,404 6,965,8827,233,924 7,007,851 6,957,921 6,457,883 6,977,751 6,398,332 6,394,5736,622,923

The disclosures of these co-pending applications are incorporated hereinby cross-reference.

Various methods, systems and apparatus relating to the present inventionare disclosed in the following co-pending applications/granted patentsfiled by the applicant or assignee of the present invention on 23 May2000:

6,428,133 6,526,658 6,315,399 6,338,548 6,540,319 6,328,425 6,991,3206,383,833 6,464,332 6,390,591 6,328,417 09/575,197 7,079,712 6,825,9457,330,974 6,987,506 7,038,797 6,980,318 6,816,274 7,102,772 7,350,2366,681,045 6,728,000 7,173,722 7,088,459 09/575,181 7,062,651 6,789,1946,789,191 6,644,642 6,502,614 6,669,385 6,549,935 6,987,573 6,727,9966,591,884 6,760,119 7,295,332 6,290,349 6,428,155 6,785,016 6,822,6396,737,591 7,055,739 7,233,320 6,830,196 6,957,768 7,456,820 7,170,4997,106,888 7,123,239 6,281,912 6,604,810 6,318,920 6,488,422 6,795,2156,859,289 6,812,972 6,804,026 7,259,889 6,975,429

The disclosures of these co-pending applications are incorporated hereinby cross-reference.

BACKGROUND

Cameras are used to capture photos. Traditional cameras capture photoson film. The film is developed and the photos are printed. The negative,i.e. the original developed film, provides a source from which newprints can be obtained. The advent of high-quality scanning also allowsa print to act as a source of copies, although not with the same qualityas from a negative. If either a negative or a print is damaged, thequality of a subsequent copy is compromised.

Digital cameras capture photos as digital images which can be bothdisplayed and printed. A digital image thus acts as a digital“negative”. However, many users find the task of printing and otherwisemanaging digital images onerous.

OBJECT

It is an object of the present invention to provide a new method andsystem for capturing and printing a photo.

SUMMARY OF INVENTION

According to a first aspect, the present invention provides a camera forcapturing an image and printing a first interface onto a first surface,in response to a user input, and for printing a second interface onto asecond surface, in response to first indicating data received from asensing device, the first indicating data being sensed by the sensingdevice from first coded data, the first interface including the firstcoded data, the camera including:

(a) a camera module, including an image sensor, configured to:

-   -   (i) receive a user input; and    -   (ii) capture, via the image sensor and in response to the user        input, the image;        (b) an input module configured to:    -   (i) receive, from the sensing device, the first indicating data,        the first indicating data being at least partially indicative of        response data;    -   (ii) generate second indicating data based on the first        indicating data, the second indicating data being at least        partially indicative of the response data;    -   (iii) send the second indicating data to a computer system; and        (c) a printing module, including a printing mechanism,        configured to:    -   (i) receive, from the camera module, the image;    -   (ii) generate the first interface based at least partially on        the image;    -   (iii) print the first interface onto the first surface using the        printing mechanism;    -   (iv) receive the response data from the computer system;    -   (v) generate the second interface based at least partially on        the response data; and    -   (vi) print the second interface onto the second surface using        the printing mechanism.

Preferably, the second interface includes second coded data, wherein theprinting module includes a coded data generator configured to generatethe second coded data based on at least part of the response data. Morepreferably, the response data includes second region identity dataindicative of at least one identity, the identity being associated witha region of the second interface, the coded data generator beingconfigured to generate the second coded data based on the second regionidentity data, the second coded data being indicative of the identity.

In a preferred embodiment, the second interface includes visibleinformation in addition to the second coded data, the visibleinformation being based at least partially on the response data.

Preferably, the second coded data is also indicative of at least onereference point of the region. More preferably, the at least onereference point is determined on the basis of a coded data layout.

Preferably, the printing module is configured to receive the coded datalayout from the computer system.

In one embodiment, the camera further includes storage means for storinga plurality of the coded data layouts, the printing module beingconfigured to:

receive, from the computer system, layout selection informationindicative of one of the coded data layouts; and

use the layout selection information to select one of the stored codedlayouts for use in determining the at least one reference point.

Preferably, the first indicating data includes location data sensed bythe sensing device from the first coded data.

In one preferred form, the first indicating data includes first regionidentity data sensed by the sensing device from the first coded data,the first region identity data being indicative of an identityassociated with a region of the first interface, the region being atleast partially indicative of the response data.

In another preferred form, the first indicating data includes locationdata sensed by the sensing device from the first coded data, thelocation data being indicative of a location within the region, thelocation within the region being at least partially indicative of theresponse data.

Preferably, the second coded data includes at least one tag, each tagbeing indicative of the identity of the region.

Further objects and advantages of the invention will be apparent fromthe detailed description that follows.

BRIEF DESCRIPTION OF DRAWINGS

Preferred and other embodiments of the invention will now be described,by way of non-limiting example only, with reference to the accompanyingdrawings, in which:

FIG. 1 is a schematic of a the relationship between a sample printednetpage and its online page description;

FIG. 2 is a schematic view of a interaction between a netpage pen, anetpage printer, a netpage page server, and a netpage applicationserver;

FIG. 3 illustrates a collection of netpage servers and printersinterconnected via a network;

FIG. 4 is a schematic view of a high-level structure of a printednetpage and its online page description;

FIG. 5 is a plan view showing a structure of a netpage tag;

FIG. 6 is a plan view showing a relationship between a set of the tagsshown in FIG. 5 and a field of view of a netpage sensing device in theform of a netpage pen;

FIG. 7 is a flowchart of a tag image processing and decoding algorithm;

FIG. 8 is a perspective view of a netpage pen and its associatedtag-sensing field-of-view cone;

FIG. 9 is a perspective exploded view of the netpage pen shown in FIG.8;

FIG. 10 is a schematic block diagram of a pen controller for the netpagepen;

FIG. 11 is a perspective view of a wall-mounted netpage printer;

FIG. 12 is a section through the length of the netpage printer of FIG.11;

FIG. 12A is an enlarged portion of FIG. 12 showing a section of theduplexed print engines and glue wheel assembly;

FIG. 13 is a detailed view of the ink cartridge, ink, air and gluepaths, and print engines of the netpage printer of FIGS. 11 and 12;

FIG. 14 is a schematic block diagram of a printer controller for thenetpage printer;

FIG. 15 is a schematic block diagram of duplexed print enginecontrollers and Memjet™ printheads associated with the printercontroller shown in FIG. 14;

FIG. 16 is a schematic block diagram of the print engine controllershown in FIGS. 14 and 15;

FIG. 17 is a perspective view of a single Memjet™ printing element, asused in, for example, the netpage printer of FIGS. 10 to 12;

FIG. 18 is a perspective view of a small part of an array of Memjet™printing elements;

FIG. 19 is a series of perspective views illustrating the operatingcycle of the Memjet™ printing element shown in FIG. 13;

FIG. 20 is a perspective view of a short segment of a pagewidth Memjet™printhead;

FIG. 21 is a schematic view of a user class diagram;

FIG. 22 is a schematic view of a printer class diagram;

FIG. 23 is a schematic view of a pen class diagram;

FIG. 24 is a schematic view of an application class diagram;

FIG. 25 is a schematic view of a document and page description classdiagram;

FIG. 26 is a schematic view of a document and page ownership classdiagram;

FIG. 27 is a schematic view of a terminal element specialization classdiagram;

FIG. 28 is a schematic view of a static element specialization classdiagram;

FIG. 29 is a schematic view of a hyperlink element class diagram;

FIG. 30 is a schematic view of a hyperlink element specialization classdiagram;

FIG. 31 is a schematic view of a hyperlinked group class diagram;

FIG. 32 is a schematic view of a form class diagram;

FIG. 33 is a schematic view of a digital ink class diagram;

FIG. 34 is a schematic view of a field element specialization classdiagram;

FIG. 35 is a schematic view of a checkbox field class diagram;

FIG. 36 is a schematic view of a text field class diagram;

FIG. 37 is a schematic view of a signature field class diagram;

FIG. 38 is a flowchart of an input processing algorithm;

FIG. 38A is a detailed flowchart of one step of the flowchart of FIG.38;

FIG. 39 is a schematic view of a page server command element classdiagram;

FIG. 40 is a schematic view of a subscription delivery protocol;

FIG. 41 is a schematic view of a hyperlink request class diagram;

FIG. 42 is a schematic view of a hyperlink activation protocol;

FIG. 43 is a schematic view of a form submission protocol;

FIG. 44 is a schematic view of a set of user interface flow documenticons;

FIG. 45 is a schematic view of a set of user interface page layoutelement icons;

FIG. 46 is a schematic view of a photo collection class diagram;

FIG. 47 is a schematic view of a photo class diagram;

FIG. 48 is a schematic view of a photo squirting user interface flow;

FIG. 49 is a schematic view of a photo browsing user interface flow;

FIG. 50 is a schematic view of a photo printing user interface flow;

FIG. 51 is a schematic view of an add squirted photos form;

FIG. 52 is a schematic view of a photo manager menu form;

FIG. 53 is a schematic view of a photo history list form;

FIG. 54 is a schematic view of a photo list form;

FIG. 55 is a schematic view of a photo folder list form;

FIG. 56 is a schematic view of a copy/move to photo folder form;

FIG. 57 is a schematic view of a photo folder form;

FIG. 58 is a schematic view of a photo thumbnails page;

FIG. 59 is a schematic view of a custom photo print form;

FIG. 60 is a perspective view of the rear of a netpage camera;

FIG. 61 is a perspective view of the front of the netpage camera;

FIG. 62 is an exploded perspective view of the netpage camera;

FIG. 63 is a perspective view of a print engine;

FIG. 64 is an exploded perspective view of the print engine;

FIG. 65 is a perspective view of the print engine with a print cartridgeused with the print engine removed;

FIG. 66 is a perspective rear view of the print engine with the printcartridge shown in ghost outline;

FIG. 67 is a perspective sectional view of the print engine;

FIG. 68 is a perspective exploded view of a printhead sub-assembly ofthe print engine;

FIG. 69 is a perspective cut-away view of the printhead sub-assembly;

FIG. 70 is a sectional end view of the printhead sub-assembly with acapping mechanism in a capped position;

FIG. 71 is a sectional end view of the printhead sub-assembly with acapping mechanism in an uncapped position;

FIG. 72 is a perspective view of the print cartridge;

FIG. 73 is a perspective exploded view of the print cartridge;

FIG. 74 is a schematic block diagram of a camera controller for thenetpage camera shown in FIGS. 60 to 62;

FIG. 75 is a schematic block diagram of a print engine controller andMemjet™ printhead associated with the camera controller shown in FIG.74;

FIG. 76 is a flowchart of photo capture processing in the netpagecamera;

FIG. 77 is a flowchart of document processing in the netpage printer andcamera;

FIG. 78 is a schematic view of a photo document class diagram;

FIG. 79 is a flowchart of photo document rasterization in the netpagecamera; and

FIG. 80 is a flowchart of dedicated photo capture and printing in thenetpage camera.

DETAILED DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

Note: Memjet™ is a trade mark of Silverbrook Research Pty Ltd,Australia.

In the preferred embodiment, the invention is configured to work withthe netpage networked computer system, a detailed overview of whichfollows. It will be appreciated that not every implementation willnecessarily embody all or even most of the specific details andextensions discussed below in relation to the basic system. However, thesystem is described in its most complete form to reduce the need forexternal reference when attempting to understand the context in whichthe preferred embodiments and aspects of the present invention operate.

In brief summary, the preferred form of the netpage system employs acomputer interface in the form of a mapped surface, that is, a physicalsurface which contains references to a map of the surface maintained ina computer system. The map references can be queried by an appropriatesensing device. Depending upon the specific implementation, the mapreferences may be encoded visibly or invisibly, and defined in such away that a local query on the mapped surface yields an unambiguous mapreference both within the map and among different maps. The computersystem can contain information about features on the mapped surface, andsuch information can be retrieved based on map references supplied by asensing device used with the mapped surface. The information thusretrieved can take the form of actions which are initiated by thecomputer system on behalf of the operator in response to the operator'sinteraction with the surface features.

In its preferred form, the netpage system relies on the production of,and human interaction with, netpages. These are pages of text, graphicsand images printed on ordinary paper, but which work like interactiveweb pages. Information is encoded on each page using ink which issubstantially invisible to the unaided human eye. The ink, however, andthereby the coded data, can be sensed by an optically imaging pen andtransmitted to the netpage system.

In the preferred form, active buttons and hyperlinks on each page can beclicked with the pen to request information from the network or tosignal preferences to a network server. In one embodiment, text writtenby hand on a netpage is automatically recognized and converted tocomputer text in the netpage system, allowing forms to be filled in. Inother embodiments, signatures recorded on a netpage are automaticallyverified, allowing e-commerce transactions to be securely authorized.

As illustrated in FIG. 1, a printed netpage 1 can represent ainteractive form which can be filled in by the user both physically, onthe printed page, and “electronically”, via communication between thepen and the netpage system. The example shows a “Request” formcontaining name and address fields and a submit button. The netpageconsists of graphic data 2 printed using visible ink, and coded data 3printed as a collection of tags 4 using invisible ink. The correspondingpage description 5, stored on the netpage network, describes theindividual elements of the netpage. In particular it describes the typeand spatial extent (zone) of each interactive element (i.e. text fieldor button in the example), to allow the netpage system to correctlyinterpret input via the netpage. The submit button 6, for example, has azone 7 which corresponds to the spatial extent of the correspondinggraphic 8.

As illustrated in FIG. 2, the netpage pen 101, a preferred form of whichis shown in FIGS. 8 and 9 and described in more detail below, works inconjunction with a netpage printer 601, an Internet-connected printingappliance for home, office or mobile use. The pen is wireless andcommunicates securely with the netpage printer via a short-range radiolink 9.

The netpage printer 601, a preferred form of which is shown in FIGS. 11to 13 and described in more detail below, is able to deliver,periodically or on demand, personalized newspapers, magazines, catalogs,brochures and other publications, all printed at high quality asinteractive netpages. Unlike a personal computer, the netpage printer isan appliance which can be, for example, wall-mounted adjacent to an areawhere the morning news is first consumed, such as in a user's kitchen,near a breakfast table, or near the household's point of departure forthe day. It also comes in tabletop, desktop, portable and miniatureversions.

Netpages printed at their point of consumption combine the ease-of-useof paper with the timeliness and interactivity of an interactive medium.

As shown in FIG. 2, the netpage pen 101 interacts with the coded data ona printed netpage 1 and communicates, via a short-range radio link 9,the interaction to a netpage printer. The printer 601 sends theinteraction to the relevant netpage page server 10 for interpretation.In appropriate circumstances, the page server sends a correspondingmessage to application computer software running on a netpageapplication server 13. The application server may in turn send aresponse which is printed on the originating printer.

The netpage system is made considerably more convenient in the preferredembodiment by being used in conjunction with high-speedmicroelectromechanical system (MEMS) based inkjet (Memjet™) printers. Inthe preferred form of this technology, relatively high-speed andhigh-quality printing is made more affordable to consumers. In itspreferred form, a netpage publication has the physical characteristicsof a traditional newsmagazine, such as a set of letter-size glossy pagesprinted in full color on both sides, bound together for easy navigationand comfortable handling.

The netpage printer exploits the growing availability of broadbandInternet access. Cable service is available to 95% of households in theUnited States, and cable modem service offering broadband Internetaccess is already available to 20% of these. The netpage printer canalso operate with slower connections, but with longer delivery times andlower image quality. Indeed, the netpage system can be enabled usingexisting consumer inkjet and laser printers, although the system willoperate more slowly and will therefore be less acceptable from aconsumer's point of view. In other embodiments, the netpage system ishosted on a private intranet. In still other embodiments, the netpagesystem is hosted on a single computer or computer-enabled device, suchas a printer.

Netpage publication servers 14 on the netpage network are configured todeliver print-quality publications to netpage printers. Periodicalpublications are delivered automatically to subscribing netpage printersvia pointcasting and multicasting Internet protocols. Personalizedpublications are filtered and formatted according to individual userprofiles.

A netpage printer can be configured to support any number of pens, and apen can work with any number of netpage printers. In the preferredimplementation, each netpage pen has a unique identifier. A householdmay have a collection of colored netpage pens, one assigned to eachmember of the family. This allows each user to maintain a distinctprofile with respect to a netpage publication server or applicationserver.

A netpage pen can also be registered with a netpage registration server11 and linked to one or more payment card accounts. This allowse-commerce payments to be securely authorized using the netpage pen. Thenetpage registration server compares the signature captured by thenetpage pen with a previously registered signature, allowing it toauthenticate the user's identity to an e-commerce server. Otherbiometrics can also be used to verify identity. A version of the netpagepen includes fingerprint scanning, verified in a similar way by thenetpage registration server.

Although a netpage printer may deliver periodicals such as the morningnewspaper without user intervention, it can be configured never todeliver unsolicited junk mail. In its preferred form, it only deliversperiodicals from subscribed or otherwise authorized sources. In thisrespect, the netpage printer is unlike a fax machine or e-mail accountwhich is visible to any junk mailer who knows the telephone number oremail address.

1 Netpage System Architecture

Each object model in the system is described using a Unified ModelingLanguage (UML) class diagram. A class diagram consists of a set ofobject classes connected by relationships, and two kinds ofrelationships are of interest here: associations and generalizations. Anassociation represents some kind of relationship between objects, i.e.between instances of classes. A generalization relates actual classes,and can be understood in the following way: if a class is thought of asthe set of all objects of that class, and class A is a generalization ofclass B, then B is simply a subset of A. The UML does not directlysupport second-order modelling—i.e. classes of classes.

Each class is drawn as a rectangle labelled with the name of the class.It contains a list of the attributes of the class, separated from thename by a horizontal line, and a list of the operations of the class,separated from the attribute list by a horizontal line. In the classdiagrams which follow, however, operations are never modelled.

An association is drawn as a line joining two classes, optionallylabelled at either end with the multiplicity of the association. Thedefault multiplicity is one. An asterisk (*) indicates a multiplicity of“many”, i.e. zero or more. Each association is optionally labelled withits name, and is also optionally labelled at either end with the role ofthe corresponding class. An open diamond indicates an aggregationassociation (“is-part-of”), and is drawn at the aggregator end of theassociation line.

A generalization relationship (“is-a”) is drawn as a solid line joiningtwo classes, with an arrow (in the form of an open triangle) at thegeneralization end.

When a class diagram is broken up into multiple diagrams, any classwhich is duplicated is shown with a dashed outline in all but the maindiagram which defines it. It is shown with attributes only where it isdefined.

1.1 Netpages

Netpages are the foundation on which a netpage network is built. Theyprovide a paper-based user interface to published information andinteractive services.

A netpage consists of a printed page (or other surface region) invisiblytagged with references to an online description of the page. The onlinepage description is maintained persistently by a netpage page server.The page description describes the visible layout and content of thepage, including text, graphics and images. It also describes the inputelements on the page, including buttons, hyperlinks, and input fields. Anetpage allows markings made with a netpage pen on its surface to besimultaneously captured and processed by the netpage system.

Multiple netpages can share the same page description. However, to allowinput through otherwise identical pages to be distinguished, eachnetpage is assigned a unique page identifier. This page ID hassufficient precision to distinguish between a very large number ofnetpages.

Each reference to the page description is encoded in a printed tag. Thetag identifies the unique page on which it appears, and therebyindirectly identifies the page description. The tag also identifies itsown position on the page. Characteristics of the tags are described inmore detail below.

Tags are printed in infrared-absorptive ink on any substrate which isinfrared-reflective, such as ordinary paper. Near-infrared wavelengthsare invisible to the human eye but are easily sensed by a solid-stateimage sensor with an appropriate filter.

A tag is sensed by an area image sensor in the netpage pen, and the tagdata is transmitted to the netpage system via the nearest netpageprinter. The pen is wireless and communicates with the netpage printervia a short-range radio link. Tags are sufficiently small and denselyarranged that the pen can reliably image at least one tag even on asingle click on the page. It is important that the pen recognize thepage ID and position on every interaction with the page, since theinteraction is stateless. Tags are error-correctably encoded to makethem partially tolerant to surface damage.

The netpage page server maintains a unique page instance for eachprinted netpage, allowing it to maintain a distinct set of user-suppliedvalues for input fields in the page description for each printednetpage.

The relationship between the page description, the page instance, andthe printed netpage is shown in FIG. 4. The printed netpage may be partof a printed netpage document 45. The page instance is associated withboth the netpage printer which printed it and, if known, the netpageuser who requested it.

1.2 Netpage Tags 1.2.1 Tag Data Content

In a preferred form, each tag identifies the region in which it appears,and the location of that tag within the region. A tag may also containflags which relate to the region as a whole or to the tag. One or moreflag bits may, for example, signal a tag sensing device to providefeedback indicative of a function associated with the immediate area ofthe tag, without the sensing device having to refer to a description ofthe region. A netpage pen may, for example, illuminate an “active area”LED when in the zone of a hyperlink.

As will be more clearly explained below, in a preferred embodiment, eachtag contains an easily recognized invariant structure which aids initialdetection, and which assists in minimizing the effect of any warpinduced by the surface or by the sensing process. The tags preferablytile the entire page, and are sufficiently small and densely arrangedthat the pen can reliably image at least one tag even on a single clickon the page. It is important that the pen recognize the page ID andposition on every interaction with the page, since the interaction isstateless.

In a preferred embodiment, the region to which a tag refers coincideswith an entire page, and the region ID encoded in the tag is thereforesynonymous with the page ID of the page on which the tag appears. Inother embodiments, the region to which a tag refers can be an arbitrarysubregion of a page or other surface. For example, it can coincide withthe zone of an interactive element, in which case the region ID candirectly identify the interactive element.

TABLE 1 Tag data Field Precision (bits) Region ID 100 Tag ID 16 Flags 4Total 120

Each tag contains 120 bits of information, typically allocated as shownin Table 1. Assuming a maximum tag density of 64 per square inch, a16-bit tag ID supports a region size of up to 1024 square inches. Largerregions can be mapped continuously without increasing the tag IDprecision simply by using abutting regions and maps. The 100-bit regionID allows 2¹⁰⁰ (˜10³⁰ or a million trillion trillion) different regionsto be uniquely identified.

1.2.2 Tag Data Encoding

The 120 bits of tag data are redundantly encoded using a (15, 5)Reed-Solomon code. This yields 360 encoded bits consisting of 6codewords of 15 4-bit symbols each. The (15, 5) code allows up to 5symbol errors to be corrected per codeword, i.e. it is tolerant of asymbol error rate of up to 33% per codeword.

Each 4-bit symbol is represented in a spatially coherent way in the tag,and the symbols of the six codewords are interleaved spatially withinthe tag. This ensures that a burst error (an error affecting multiplespatially adjacent bits) damages a minimum number of symbols overall anda minimum number of symbols in any one codeword, thus maximising thelikelihood that the burst error can be fully corrected.

1.2.3 Physical Tag Structure

The physical representation of the tag, shown in FIG. 5, includes fixedtarget structures 15, 16, 17 and variable data areas 18. The fixedtarget structures allow a sensing device such as the netpage pen todetect the tag and infer its three-dimensional orientation relative tothe sensor. The data areas contain representations of the individualbits of the encoded tag data.

To achieve proper tag reproduction, the tag is rendered at a resolutionof 256×256 dots. When printed at 1600 dots per inch this yields a tagwith a diameter of about 4 mm. At this resolution the tag is designed tobe surrounded by a “quiet area” of radius 16 dots. Since the quiet areais also contributed by adjacent tags, it only adds 16 dots to theeffective diameter of the tag.

The tag includes six target structures. A detection ring 15 allows thesensing device to initially detect the tag. The ring is easy to detectbecause it is rotationally invariant and because a simple correction ofits aspect ratio removes most of the effects of perspective distortion.An orientation axis 16 allows the sensing device to determine theapproximate planar orientation of the tag due to the yaw of the sensor.The orientation axis is skewed to yield a unique orientation. Fourperspective targets 17 allow the sensing device to infer an accuratetwo-dimensional perspective transform of the tag and hence an accuratethree-dimensional position and orientation of the tag relative to thesensor.

All target structures are redundantly large to improve their immunity tonoise.

The overall tag shape is circular. This supports, amongst other things,optimal tag packing on an irregular triangular grid. In combination withthe circular detection ring, this makes a circular arrangement of databits within the tag optimal. To maximise its size, each data bit isrepresented by a radial wedge in the form of an area bounded by tworadial lines and two concentric circular arcs. Each wedge has a minimumdimension of 8 dots at 1600 dpi and is designed so that its base (itsinner arc), is at least equal to this minimum dimension. The height ofthe wedge in the radial direction is always equal to the minimumdimension. Each 4-bit data symbol is represented by an array of 2×2wedges.

The 15 4-bit data symbols of each of the six codewords are allocated tothe four concentric symbol rings 18 a to 18 d in interleaved fashion.Symbols are allocated alternately in circular progression around thetag.

The interleaving is designed to maximise the average spatial distancebetween any two symbols of the same codeword.

In order to support “single-click” interaction with a tagged region viaa sensing device, the sensing device must be able to see at least oneentire tag in its field of view no matter where in the region or at whatorientation it is positioned. The required diameter of the field of viewof the sensing device is therefore a function of the size and spacing ofthe tags.

Assuming a circular tag shape, the minimum diameter of the sensor fieldof view is obtained when the tags are tiled on a equilateral triangulargrid, as shown in FIG. 6.

1.2.4 Tag Image Processing and Decoding

The tag image processing and decoding performed by a sensing device suchas the netpage pen is shown in FIG. 7. While a captured image is beingacquired from the image sensor, the dynamic range of the image isdetermined (at 20). The center of the range is then chosen as the binarythreshold for the image 21. The image is then thresholded and segmentedinto connected pixel regions (i.e. shapes 23) (at 22). Shapes which aretoo small to represent tag target structures are discarded. The size andcentroid of each shape is also computed.

Binary shape moments 25 are then computed (at 24) for each shape, andthese provide the basis for subsequently locating target structures.Central shape moments are by their nature invariant of position, and canbe easily made invariant of scale, aspect ratio and rotation.

The ring target structure 15 is the first to be located (at 26). A ringhas the advantage of being very well behaved when perspective-distorted.Matching proceeds by aspect-normalizing and rotation-normalizing eachshape's moments. Once its second-order moments are normalized the ringis easy to recognize even if the perspective distortion was significant.The ring's original aspect and rotation 27 together provide a usefulapproximation of the perspective transform.

The axis target structure 16 is the next to be located (at 28). Matchingproceeds by applying the ring's normalizations to each shape's moments,and rotation-normalizing the resulting moments. Once its second-ordermoments are normalized the axis target is easily recognized. Note thatone third order moment is required to disambiguate the two possibleorientations of the axis. The shape is deliberately skewed to one sideto make this possible. Note also that it is only possible torotation-normalize the axis target after it has had the ring'snormalizations applied, since the perspective distortion can hide theaxis target's axis. The axis target's original rotation provides auseful approximation of the tag's rotation due to pen yaw 29.

The four perspective target structures 17 are the last to be located (at30). Good estimates of their positions are computed based on their knownspatial relationships to the ring and axis targets, the aspect androtation of the ring, and the rotation of the axis. Matching proceeds byapplying the ring's normalizations to each shape's moments. Once theirsecond-order moments are normalized the circular perspective targets areeasy to recognize, and the target closest to each estimated position istaken as a match. The original centroids of the four perspective targetsare then taken to be the perspective-distorted corners 31 of a square ofknown size in tag space, and an eight-degree-of-freedom perspectivetransform 33 is inferred (at 32) based on solving the well-understoodequations relating the four tag-space and image-space point pairs (seeHeckbert, P., Fundamentals of Texture Mapping and Image Warping, MastersThesis, Dept. of EECS, U. of California at Berkeley, Technical ReportNo. UCB/CSD 89/516, June 1989, the contents of which are hereinincorporated by cross-reference).

The inferred tag-space to image-space perspective transform is used toproject (at 36) each known data bit position in tag space into imagespace where the real-valued position is used to bilinearly interpolate(at 36) the four relevant adjacent pixels in the input image. Thepreviously computed image threshold 21 is used to threshold the resultto produce the final bit value 37.

Once all 360 data bits 37 have been obtained in this way, each of thesix 60-bit Reed-Solomon codewords is decoded (at 38) to yield 20 decodedbits 39, or 120 decoded bits in total. Note that the codeword symbolsare sampled in codeword order, so that codewords are implicitlyde-interleaved during the sampling process.

The ring target 15 is only sought in a subarea of the image whoserelationship to the image guarantees that the ring, if found, is part ofa complete tag. If a complete tag is not found and successfully decoded,then no pen position is recorded for the current frame. Given adequateprocessing power and ideally a non-minimal field of view 193, analternative strategy involves seeking another tag in the current image.

The obtained tag data indicates the identity of the region containingthe tag and the position of the tag within the region. An accurateposition 35 of the pen nib in the region, as well as the overallorientation 35 of the pen, is then inferred (at 34) from the perspectivetransform 33 observed on the tag and the known spatial relationshipbetween the pen's physical axis and the pen's optical axis.

1.2.5 Tag Map

Decoding a tag results in a region ID, a tag ID, and a tag-relative pentransform. Before the tag ID and the tag-relative pen location can betranslated into an absolute location within the tagged region, thelocation of the tag within the region must be known. This is given by atag map, a function which maps each tag ID in a tagged region to acorresponding location. The tag map class diagram is shown in FIG. 22,as part of the netpage printer class diagram.

A tag map reflects the scheme used to tile the surface region with tags,and this can vary according to surface type. When multiple taggedregions share the same tiling scheme and the same tag numbering scheme,they can also share the same tag map.

The tag map for a region must be retrievable via the region ID. Thus,given a region ID, a tag ID and a pen transform, the tag map can beretrieved, the tag ID can be translated into an absolute tag locationwithin the region, and the tag-relative pen location can be added to thetag location to yield an absolute pen location within the region.

1.2.6 Tagging Schemes

Two distinct surface coding schemes are of interest, both of which usethe tag structure described earlier in this section. The preferredcoding scheme uses “location-indicating” tags as already discussed. Analternative coding scheme uses object-indicating tags.

A location-indicating tag contains a tag ID which, when translatedthrough the tag map associated with the tagged region, yields a uniquetag location within the region. The tag-relative location of the pen isadded to this tag location to yield the location of the pen within theregion. This in turn is used to determine the location of the penrelative to a user interface element in the page description associatedwith the region. Not only is the user interface element itselfidentified, but a location relative to the user interface element isidentified. Location-indicating tags therefore trivially support thecapture of an absolute pen path in the zone of a particular userinterface element.

An object-indicating tag contains a tag ID which directly identifies auser interface element in the page description associated with theregion. All the tags in the zone of the user interface element identifythe user interface element, making them all identical and thereforeindistinguishable. Object-indicating tags do not, therefore, support thecapture of an absolute pen path. They do, however, support the captureof a relative pen path. So long as the position sampling frequencyexceeds twice the encountered tag frequency, the displacement from onesampled pen position to the next within a stroke can be unambiguouslydetermined.

With either tagging scheme, the tags function in cooperation withassociated visual elements on the netpage as user interactive elementsin that a user can interact with the printed page using an appropriatesensing device in order for tag data to be read by the sensing deviceand for an appropriate response to be generated in the netpage system.

1.3 Document and Page Descriptions

A preferred embodiment of a document and page description class diagramis shown in FIGS. 25 and 26.

In the netpage system a document is described at three levels. At themost abstract level the document 836 has a hierarchical structure whoseterminal elements 839 are associated with content objects 840 such astext objects, text style objects, image objects, etc. Once the documentis printed on a printer with a particular page size and according to aparticular user's scale factor preference, the document is paginated andotherwise formatted. Formatted terminal elements 835 will in some casesbe associated with content objects which are different from thoseassociated with their corresponding terminal elements, particularlywhere the content objects are style-related. Each printed instance of adocument and page is also described separately, to allow input capturedthrough a particular page instance 830 to be recorded separately frominput captured through other instances of the same page description.

The presence of the most abstract document description on the pageserver allows a user to request a copy of a document without beingforced to accept the source document's specific format. The user may berequesting a copy through a printer with a different page size, forexample. Conversely, the presence of the formatted document descriptionon the page server allows the page server to efficiently interpret useractions on a particular printed page.

A formatted document 834 consists of a set of formatted pagedescriptions 5, each of which consists of a set of formatted terminalelements 835. Each formatted element has a spatial extent or zone 58 onthe page. This defines the active area of input elements such ashyperlinks and input fields.

A document instance 831 corresponds to a formatted document 834. Itconsists of a set of page instances 830, each of which corresponds to apage description 5 of the formatted document. Each page instance 830describes a single unique printed netpage 1, and records the page ID 50of the netpage. A page instance is not part of a document instance if itrepresents a copy of a page requested in isolation.

A page instance consists of a set of terminal element instances 832. Anelement instance only exists if it records instance-specificinformation. Thus, a hyperlink instance exists for a hyperlink elementbecause it records a transaction ID 55 which is specific to the pageinstance, and a field instance exists for a field element because itrecords input specific to the page instance. An element instance doesnot exist, however, for static elements such as textflows.

A terminal element can be a static element 843, a hyperlink element 844,a field element 845 or a page server command element 846, as shown inFIG. 27. A static element 843 can be a style element 847 with anassociated style object 854, a textflow element 848 with an associatedstyled text object 855, an image element 849 with an associated imageelement 856, a graphic element 850 with an associated graphic object857, a video clip element 851 with an associated video clip object 858,an audio clip element 852 with an associated audio clip object 859, or ascript element 853 with an associated script object 860, as shown inFIG. 28.

A page instance has a background field 833 which is used to record anydigital ink captured on the page which does not apply to a specificinput element.

In the preferred form of the invention, a tag map 811 is associated witheach page instance to allow tags on the page to be translated intolocations on the page.

1.4 The Netpage Network

In a preferred embodiment, a netpage network consists of a distributedset of netpage page servers 10, netpage registration servers 11, netpageID servers 12, netpage application servers 13, netpage publicationservers 14, and netpage printers 601 connected via a network 19 such asthe Internet, as shown in FIG. 3.

The netpage registration server 11 is a server which recordsrelationships between users, pens, printers, applications andpublications, and thereby authorizes various network activities. Itauthenticates users and acts as a signing proxy on behalf ofauthenticated users in application transactions. It also provideshandwriting recognition services. As described above, a netpage pageserver 10 maintains persistent information about page descriptions andpage instances. The netpage network includes any number of page servers,each handling a subset of page instances. Since a page server alsomaintains user input values for each page instance, clients such asnetpage printers send netpage input directly to the appropriate pageserver. The page server interprets any such input relative to thedescription of the corresponding page.

A netpage ID server 12 allocates document IDs 51 on demand, and providesload-balancing of page servers via its ID allocation scheme.

A netpage printer uses the Internet Distributed Name System (DNS), orsimilar, to resolve a netpage page ID 50 into the network address of thenetpage page server handling the corresponding page instance.

A netpage application server 13 is a server which hosts interactivenetpage applications. A netpage publication server 14 is an applicationserver which publishes netpage documents to netpage printers. They aredescribed in detail in Section 2.

Netpage servers can be hosted on a variety of network server platformsfrom manufacturers such as IBM, Hewlett-Packard, and Sun. Multiplenetpage servers can run concurrently on a single host, and a singleserver can be distributed over a number of hosts. Some or all of thefunctionality provided by netpage servers, and in particular thefunctionality provided by the ID server and the page server, can also beprovided directly in a netpage appliance such as a netpage printer, in acomputer workstation, or on a local network.

1.5 The Netpage Printer

The netpage printer 601 is an appliance which is registered with thenetpage system and prints netpage documents on demand and viasubscription. Each printer has a unique printer ID 62, and is connectedto the netpage network via a network such as the Internet, ideally via abroadband connection.

Apart from identity and security settings in non-volatile memory, thenetpage printer contains no persistent storage. As far as a user isconcerned, “the network is the computer”. Netpages functioninteractively across space and time with the help of the distributednetpage page servers 10, independently of particular netpage printers.

The netpage printer receives subscribed netpage documents from netpagepublication servers 14. Each document is distributed in two parts: thepage layouts, and the actual text and image objects which populate thepages. Because of personalization, page layouts are typically specificto a particular subscriber and so are pointcast to the subscriber'sprinter via the appropriate page server. Text and image objects, on theother hand, are typically shared with other subscribers, and so aremulticast to all subscribers' printers and the appropriate page servers.

The netpage publication server optimizes the segmentation of documentcontent into pointcasts and multicasts. After receiving the pointcast ofa document's page layouts, the printer knows which multicasts, if any,to listen to.

Once the printer has received the complete page layouts and objects thatdefine the document to be printed, it can print the document.

The printer rasterizes and prints odd and even pages simultaneously onboth sides of the sheet. It contains duplexed print engine controllers760 and print engines utilizing Memjet™ printheads 350 for this purpose.

The printing process consists of two decoupled stages: rasterization ofpage descriptions, and expansion and printing of page images. The rasterimage processor (RIP) consists of one or more standard DSPs 757 runningin parallel. The duplexed print engine controllers consist of customprocessors which expand, dither and print page images in real time,synchronized with the operation of the printheads in the print engines.Printers not enabled for IR printing have the option to print tags usingIR-absorptive black ink, although this restricts tags to otherwise emptyareas of the page.

Although such pages have more limited functionality than IR-printedpages, they are still classed as netpages.

A normal netpage printer prints netpages on sheets of paper. Morespecialised netpage printers may print onto more specialised surfaces,such as globes. Each printer supports at least one surface type, andsupports at least one tag tiling scheme, and hence tag map, for eachsurface type. The tag map 811 which describes the tag tiling schemeactually used to print a document becomes associated with that documentso that the document's tags can be correctly interpreted.

FIG. 2 shows the netpage printer class diagram, reflectingprinter-related information maintained by a registration server 11 onthe netpage network.

A preferred embodiment of the netpage printer is described in greaterdetail in Section 6 below, with reference to FIGS. 11 to 16.

1.5.1 Memjet™ Printheads

The netpage system can operate using printers made with a wide range ofdigital printing technologies, including thermal inkjet, piezoelectricinkjet, laser electrophotographic, and others. However, for wideconsumer acceptance, it is desirable that a netpage printer have thefollowing characteristics:

photographic quality color printing

high quality text printing

high reliability

low printer cost

low ink cost

low paper cost

simple operation

nearly silent printing

high printing speed

simultaneous double sided printing

compact form factor

low power consumption

No commercially available printing technology has all of thesecharacteristics.

To enable to production of printers with these characteristics, thepresent applicant has invented a new print technology, referred to asMemjet™ technology. Memjet™ is a drop-on-demand inkjet technology thatincorporates pagewidth printheads fabricated usingmicroelectromechanical systems (MEMS) technology. FIG. 17 shows a singleprinting element 300 of a Memjet™ printhead. The netpage wallprinterincorporates 168960 printing elements 300 to form a 1600 dpi pagewidthduplex printer. This printer simultaneously prints cyan, magenta,yellow, black, and infrared inks as well as paper conditioner and inkfixative.

The printing element 300 is approximately 110 microns long by 32 micronswide. Arrays of these printing elements are formed on a siliconsubstrate 301 that incorporates CMOS logic, data transfer, timing, anddrive circuits (not shown).

Major elements of the printing element 300 are the nozzle 302, thenozzle rim 303, the nozzle chamber 304, the fluidic seal 305, the inkchannel rim 306, the lever arm 307, the active actuator beam pair 308,the passive actuator beam pair 309, the active actuator anchor 310, thepassive actuator anchor 311, and the ink inlet 312.

The active actuator beam pair 308 is mechanically joined to the passiveactuator beam pair 309 at the join 319. Both beams pairs are anchored attheir respective anchor points 310 and 311. The combination of elements308, 309, 310, 311, and 319 form a cantilevered electrothermal bendactuator 320.

FIG. 18 shows a small part of an array of printing elements 300,including a cross section 315 of a printing element 300. The crosssection 315 is shown without ink, to clearly show the ink inlet 312 thatpasses through the silicon wafer 301.

FIGS. 19(A), 19(B) and 19(C) show the operating cycle of a Memjet™printing element 300.

FIG. 19(A) shows the quiescent position of the ink meniscus 316 prior toprinting an ink droplet. Ink is retained in the nozzle chamber bysurface tension at the ink meniscus 316 and at the fluidic seal 305formed between the nozzle chamber 304 and the ink channel rim 306.

While printing, the printhead CMOS circuitry distributes data from theprint engine controller to the correct printing element, latches thedata, and buffers the data to drive the electrodes 318 of the activeactuator beam pair 308. This causes an electrical current to passthrough the beam pair 308 for about one microsecond, resulting in Jouleheating. The temperature increase resulting from Joule heating causesthe beam pair 308 to expand. As the passive actuator beam pair 309 isnot heated, it does not expand, resulting in a stress difference betweenthe two beam pairs. This stress difference is partially resolved by thecantilevered end of the electrothermal bend actuator 320 bending towardsthe substrate 301. The lever arm 307 transmits this movement to thenozzle chamber 304. The nozzle chamber 304 moves about two microns tothe position shown in FIG. 19(B). This increases the ink pressure,forcing ink 321 out of the nozzle 302, and causing the ink meniscus 316to bulge. The nozzle rim 303 prevents the ink meniscus 316 fromspreading across the surface of the nozzle chamber 304.

As the temperature of the beam pairs 308 and 309 equalizes, the actuator320 returns to its original position. This aids in the break-off of theink droplet 317 from the ink 321 in the nozzle chamber, as shown in FIG.19(C). The nozzle chamber is refilled by the action of the surfacetension at the meniscus 316.

FIG. 20 shows a segment of a printhead 350. In a netpage printer, thelength of the printhead is the full width of the paper (typically 210mm) in the direction 351. The segment shown is 0.4 mm long (about 0.2%of a complete printhead). When printing, the paper is moved past thefixed printhead in the direction 352. The printhead has 6 rows ofinterdigitated printing elements 300, printing the six colors or typesof ink supplied by the ink inlets 312.

To protect the fragile surface of the printhead during operation, anozzle guard wafer 330 is attached to the printhead substrate 301. Foreach nozzle 302 there is a corresponding nozzle guard hole 331 throughwhich the ink droplets are fired. To prevent the nozzle guard holes 331from becoming blocked by paper fibers or other debris, filtered air ispumped through the air inlets 332 and out of the nozzle guard holesduring printing. To prevent ink 321 from drying, the nozzle guard issealed while the printer is idle.

1.6 The Netpage Pen

The active sensing device of the netpage system is typically a pen 101,which, using its embedded controller 134, is able to capture and decodeIR position tags from a page via an image sensor. The image sensor is asolid-state device provided with an appropriate filter to permit sensingat only near-infrared wavelengths. As described in more detail below,the system is able to sense when the nib is in contact with the surface,and the pen is able to sense tags at a sufficient rate to capture humanhandwriting (i.e. at 200 dpi or greater and 100 Hz or faster).Information captured by the pen is encrypted and wirelessly transmittedto the printer (or base station), the printer or base stationinterpreting the data with respect to the (known) page structure.

The preferred embodiment of the netpage pen operates both as a normalmarking ink pen and as a non-marking stylus. The marking aspect,however, is not necessary for using the netpage system as a browsingsystem, such as when it is used as an Internet interface. Each netpagepen is registered with the netpage system and has a unique pen ID 61.FIG. 23 shows the netpage pen class diagram, reflecting pen-relatedinformation maintained by a registration server 11 on the netpagenetwork.

When either nib is in contact with a netpage, the pen determines itsposition and orientation relative to the page. The nib is attached to aforce sensor, and the force on the nib is interpreted relative to athreshold to indicate whether the pen is “up” or “down”. This allows ainteractive element on the page to be ‘clicked’ by pressing with the pennib, in order to request, say, information from a network. Furthermore,the force is captured as a continuous value to allow, say, the fulldynamics of a signature to be verified.

The pen determines the position and orientation of its nib on thenetpage by imaging, in the infrared spectrum, an area 193 of the page inthe vicinity of the nib. It decodes the nearest tag and computes theposition of the nib relative to the tag from the observed perspectivedistortion on the imaged tag and the known geometry of the pen optics.Although the position resolution of the tag may be low, because the tagdensity on the page is inversely proportional to the tag size, theadjusted position resolution is quite high, exceeding the minimumresolution required for accurate handwriting recognition.

Pen actions relative to a netpage are captured as a series of strokes. Astroke consists of a sequence of time-stamped pen positions on the page,initiated by a pen-down event and completed by the subsequent pen-upevent. A stroke is also tagged with the page ID 50 of the netpagewhenever the page ID changes, which, under normal circumstances, is atthe commencement of the stroke.

Each netpage pen has a current selection 826 associated with it,allowing the user to perform copy and paste operations etc. Theselection is timestamped to allow the system to discard it after adefined time period. The current selection describes a region of a pageinstance. It consists of the most recent digital ink stroke capturedthrough the pen relative to the background area of the page. It isinterpreted in an application-specific manner once it is submitted to anapplication via a selection hyperlink activation.

Each pen has a current nib 824. This is the nib last notified by the pento the system. In the case of the default netpage pen described above,either the marking black ink nib or the non-marking stylus nib iscurrent. Each pen also has a current nib style 825. This is the nibstyle last associated with the pen by an application, e.g. in responseto the user selecting a color from a palette. The default nib style isthe nib style associated with the current nib. Strokes captured througha pen are tagged with the current nib style. When the strokes aresubsequently reproduced, they are reproduced in the nib style with whichthey are tagged.

Whenever the pen is within range of a printer with which it cancommunicate, the pen slowly flashes its “online” LED. When the pen failsto decode a stroke relative to the page, it momentarily activates its“error” LED. When the pen succeeds in decoding a stroke relative to thepage, it momentarily activates its “ok” LED.

A sequence of captured strokes is referred to as digital ink. Digitalink forms the basis for the digital exchange of drawings andhandwriting, for online recognition of handwriting, and for onlineverification of signatures.

The pen is wireless and transmits digital ink to the netpage printer viaa short-range radio link. The transmitted digital ink is encrypted forprivacy and security and packetized for efficient transmission, but isalways flushed on a pen-up event to ensure timely handling in theprinter.

When the pen is out-of-range of a printer it buffers digital ink ininternal memory, which has a capacity of over ten minutes of continuoushandwriting. When the pen is once again within range of a printer, ittransfers any buffered digital ink.

A pen can be registered with any number of printers, but because allstate data resides in netpages both on paper and on the network, it islargely immaterial which printer a pen is communicating with at anyparticular time.

A preferred embodiment of the pen is described in greater detail inSection 6 below, with reference to FIGS. 8 to 10.

1.7 Netpage Interaction

The netpage printer 601 receives data relating to a stroke from the pen101 when the pen is used to interact with a netpage 1. The coded data 3of the tags 4 is read by the pen when it is used to execute a movement,such as a stroke. The data allows the identity of the particular pageand associated interactive element to be determined and an indication ofthe relative positioning of the pen relative to the page to be obtained.The indicating data is transmitted to the printer, where it resolves,via the DNS, the page ID 50 of the stroke into the network address ofthe netpage page server 10 which maintains the corresponding pageinstance 830. It then transmits the stroke to the page server. If thepage was recently identified in an earlier stroke, then the printer mayalready have the address of the relevant page server in its cache. Eachnetpage consists of a compact page layout maintained persistently by anetpage page server (see below). The page layout refers to objects suchas images, fonts and pieces of text, typically stored elsewhere on thenetpage network.

When the page server receives the stroke from the pen, it retrieves thepage description to which the stroke applies, and determines whichelement of the page description the stroke intersects. It is then ableto interpret the stroke in the context of the type of the relevantelement.

A “click” is a stroke where the distance and time between the pen downposition and the subsequent pen up position are both less than somesmall maximum. An object which is activated by a click typicallyrequires a click to be activated, and accordingly, a longer stroke isignored. The failure of a pen action, such as a “sloppy” click, toregister is indicated by the lack of response from the pen's “ok” LED.

There are two kinds of input elements in a netpage page description:hyperlinks and form fields. Input through a form field can also triggerthe activation of an associated hyperlink.

1.7.1 Hyperlinks

A hyperlink is a means of sending a message to a remote application, andtypically elicits a printed response in the netpage system.

A hyperlink element 844 identifies the application 71 which handlesactivation of the hyperlink, a link ID 54 which identifies the hyperlinkto the application, an “alias required” flag which asks the system toinclude the user's application alias ID 65 in the hyperlink activation,and a description which is used when the hyperlink is recorded as afavorite or appears in the user's history. The hyperlink element classdiagram is shown in FIG. 29.

When a hyperlink is activated, the page server sends a request to anapplication somewhere on the network. The application is identified byan application ID 64, and the application ID is resolved in the normalway via the DNS. There are three types of hyperlinks: general hyperlinks863, form hyperlinks 865, and selection hyperlinks 864, as shown in FIG.30. A general hyperlink can implement a request for a linked document,or may simply signal a preference to a server. A form hyperlink submitsthe corresponding form to the application. A selection hyperlink submitsthe current selection to the application. If the current selectioncontains a single-word piece of text, for example, the application mayreturn a single-page document giving the word's meaning within thecontext in which it appears, or a translation into a different language.Each hyperlink type is characterized by what information is submitted tothe application.

The corresponding hyperlink instance 862 records a transaction ID 55which can be specific to the page instance on which the hyperlinkinstance appears. The transaction ID can identify user-specific data tothe application, for example a “shopping cart” of pending purchasesmaintained by a purchasing application on behalf of the user.

The system includes the pen's current selection 826 in a selectionhyperlink activation. The system includes the content of the associatedform instance 868 in a form hyperlink activation, although if thehyperlink has its “submit delta” attribute set, only input since thelast form submission is included. The system includes an effectivereturn path in all hyperlink activations.

A hyperlinked group 866 is a group element 838 which has an associatedhyperlink, as shown in FIG. 31. When input occurs through any fieldelement in the group, the hyperlink 844 associated with the group isactivated. A hyperlinked group can be used to associate hyperlinkbehavior with a field such as a checkbox. It can also be used, inconjunction with the “submit delta” attribute of a form hyperlink, toprovide continuous input to an application. It can therefore be used tosupport a “blackboard” interaction model, i.e. where input is capturedand therefore shared as soon as it occurs.

1.7.2 Forms

A form defines a collection of related input fields used to capture arelated set of inputs through a printed netpage. A form allows a user tosubmit one or more parameters to an application software program runningon a server.

A form 867 is a group element 838 in the document hierarchy. Itultimately contains a set of terminal field elements 839. A forminstance 868 represents a printed instance of a form. It consists of aset of field instances 870 which correspond to the field elements 845 ofthe form. Each field instance has an associated value 871, whose typedepends on the type of the corresponding field element. Each field valuerecords input through a particular printed form instance, i.e. throughone or more printed netpages. The form class diagram is shown in FIG.32.

Each form instance has a status 872 which indicates whether the form isactive, frozen, submitted, void or expired. A form is active when firstprinted. A form becomes frozen once it is signed or once its freeze timeis reached. A form becomes submitted once one of its submissionhyperlinks has been activated, unless the hyperlink has its “submitdelta” attribute set. A form becomes void when the user invokes a voidform, reset form or duplicate form page command. A form expires when itsspecified expiry time is reached, i.e. when the time the form has beenactive exceeds the form's specified lifetime. While the form is active,form input is allowed. Input through a form which is not active isinstead captured in the background field 833 of the relevant pageinstance. When the form is active or frozen, form submission is allowed.Any attempt to submit a form when the form is not active or frozen isrejected, and instead elicits an form status report.

Each form instance is associated (at 59) with any form instances derivedfrom it, thus providing a version history. This allows all but thelatest version of a form in a particular time period to be excluded froma search.

All input is captured as digital ink. Digital ink 873 consists of a setof timestamped stroke groups 874, each of which consists of a set ofstyled strokes 875. Each stroke consists of a set of timestamped penpositions 876, each of which also includes pen orientation and nibforce. The digital ink class diagram is shown in FIG. 33.

A field element 845 can be a checkbox field 877, a text field 878, adrawing field 879, or a signature field 880. The field element classdiagram is shown in FIG. 34. Any digital ink captured in a field's zone58 is assigned to the field.

A checkbox field has an associated boolean value 881, as shown in FIG.35. Any mark (a tick, a cross, a stroke, a fill zigzag, etc.) capturedin a checkbox field's zone causes a true value to be assigned to thefield's value.

A text field has an associated text value 882, as shown in FIG. 36. Anydigital ink captured in a text field's zone is automatically convertedto text via online handwriting recognition, and the text is assigned tothe field's value. Online handwriting recognition is well-understood(see, for example, Tappert, C., C. Y. Suen and T. Wakahara, “The Stateof the Art in On-Line Handwriting Recognition”, IEEE Transactions onPattern Analysis and Machine Intelligence, Vol. 12, No. 8, August 1990,the contents of which are herein incorporated by cross-reference).

A signature field has an associated digital signature value 883, asshown in FIG. 37. Any digital ink captured in a signature field's zoneis automatically verified with respect to the identity of the owner ofthe pen, and a digital signature of the content of the form of which thefield is part is generated and assigned to the field's value. Thedigital signature is generated using the pen user's private signaturekey specific to the application which owns the form. Online signatureverification is well-understood (see, for example, Plamondon, R. and G.Lorette, “Automatic Signature Verification and Writer Identification—TheState of the Art”, Pattern Recognition, Vol. 22, No. 2, 1989, thecontents of which are herein incorporated by cross-reference).

A field element is hidden if its “hidden” attribute is set. A hiddenfield element does not have an input zone on a page and does not acceptinput. It can have an associated field value which is included in theform data when the form containing the field is submitted.

“Editing” commands, such as strike-throughs indicating deletion, canalso be recognized in form fields.

Because the handwriting recognition algorithm works “online” (i.e. withaccess to the dynamics of the pen movement), rather than “offline” (i.e.with access only to a bitmap of pen markings), it can recognize run-ondiscretely-written characters with relatively high accuracy, without awriter-dependent training phase. A writer-dependent model of handwritingis automatically generated over time, however, and can be generatedup-front if necessary,

Digital ink, as already stated, consists of a sequence of strokes. Anystroke which starts in a particular element's zone is appended to thatelement's digital ink stream, ready for interpretation. Any stroke notappended to an object's digital ink stream is appended to the backgroundfield's digital ink stream.

Digital ink captured in the background field is interpreted as aselection gesture. Circumscription of one or more objects is generallyinterpreted as a selection of the circumscribed objects, although theactual interpretation is application-specific.

Table 2 summarises these various pen interactions with a netpage.

TABLE 2 Summary of pen interactions with a netpage Object Type Pen inputAction Hyperlink General Click Submit action to application Form ClickSubmit form to application Selection Click Submit selection toapplication Form field Checkbox Any mark Assign true to field TextHandwriting Convert digital ink to text; assign text to field DrawingDigital ink Assign digital ink to field Signature Signature Verifydigital ink signature; generate digital signature of form; assigndigital signature to field None — Circumscription Assign digital ink tocurrent selection

The system maintains a current selection for each pen. The selectionconsists simply of the most recent stroke captured in the backgroundfield. The selection is cleared after an inactivity timeout to ensurepredictable behavior.

The raw digital ink captured in every field is retained on the netpagepage server and is optionally transmitted with the form data when theform is submitted to the application. This allows the application tointerrogate the raw digital ink should it suspect the originalconversion, such as the conversion of handwritten text. This can, forexample, involve human intervention at the application level for formswhich fail certain application-specific consistency checks. As anextension to this, the entire background area of a form can bedesignated as a drawing field. The application can then decide, on thebasis of the presence of digital ink outside the explicit fields of theform, to route the form to a human operator, on the assumption that theuser may have indicated amendments to the filled-in fields outside ofthose fields.

FIG. 38 shows a flowchart of the process of handling pen input relativeto a netpage. The process consists of receiving (at 884) a stroke fromthe pen; identifying (at 885) the page instance 830 to which the page ID50 in the stroke refers; retrieving (at 886) the page description 5;identifying (at 887) a formatted element 839 whose zone 58 the strokeintersects; determining (at 888) whether the formatted elementcorresponds to a field element, and if so appending (at 892) thereceived stroke to the digital ink of the field value 871, interpreting(at 893) the accumulated digital ink of the field, and determining (at894) whether the field is part of a hyperlinked group 866 and if soactivating (at 895) the associated hyperlink; alternatively determining(at 889) whether the formatted element corresponds to a hyperlinkelement and if so activating (at 895) the corresponding hyperlink;alternatively, in the absence of an input field or hyperlink, appending(at 890) the received stroke to the digital ink of the background field833; and copying (at 891) the received stroke to the current selection826 of the current pen, as maintained by the registration server.

FIG. 38A shows a detailed flowchart of step 893 in the process shown inFIG. 38, where the accumulated digital ink of a field is interpretedaccording to the type of the field. The process consists of determining(at 896) whether the field is a checkbox and (at 897) whether thedigital ink represents a checkmark, and if so assigning (at 898) a truevalue to the field value; alternatively determining (at 899) whether thefield is a text field and if so converting (at 900) the digital ink tocomputer text, with the help of the appropriate registration server, andassigning (at 901) the converted computer text to the field value;alternatively determining (at 902) whether the field is a signaturefield and if so verifying (at 903) the digital ink as the signature ofthe pen's owner, with the help of the appropriate registration server,creating (at 904) a digital signature of the contents of thecorresponding form, also with the help of the registration server andusing the pen owner's private signature key relating to thecorresponding application, and assigning (at 905) the digital signatureto the field value.

1.7.3 Page Server Commands

A page server command is a command which is handled locally by the pageserver. It operates directly on form, page and document instances. Apage server command 907 can be a void form command 908, a duplicate formcommand 909, a reset form command 910, a get form status command 911, aduplicate page command 912, a reset page command 913, a get page statuscommand 914, a duplicate document command 915, a reset document command916, or a get document status command 917, as shown in FIG. 39.

A void form command voids the corresponding form instance. A duplicateform command voids the corresponding form instance and then produces anactive printed copy of the current form instance with field valuespreserved. The copy contains the same hyperlink transaction IDs as theoriginal, and so is indistinguishable from the original to anapplication. A reset form command voids the corresponding form instanceand then produces an active printed copy of the form instance with fieldvalues discarded. A get form status command produces a printed report onthe status of the corresponding form instance, including who publishedit, when it was printed, for whom it was printed, and the form status ofthe form instance.

Since a form hyperlink instance contains a transaction ID, theapplication has to be involved in producing a new form instance. Abutton requesting a new form instance is therefore typically implementedas a hyperlink.

A duplicate page command produces a printed copy of the correspondingpage instance with the background field value preserved. If the pagecontains a form or is part of a form, then the duplicate page command isinterpreted as a duplicate form command. A reset page command produces aprinted copy of the corresponding page instance with the backgroundfield value discarded. If the page contains a form or is part of a form,then the reset page command is interpreted as a reset form command. Aget page status command produces a printed report on the status of thecorresponding page instance, including who published it, when it wasprinted, for whom it was printed, and the status of any forms itcontains or is part of.

The netpage logo which appears on every netpage is usually associatedwith a duplicate page element.

When a page instance is duplicated with field values preserved, fieldvalues are printed in their native form, i.e. a checkmark appears as astandard checkmark graphic, and text appears as typeset text. Onlydrawings and signatures appear in their original form, with a signatureaccompanied by a standard graphic indicating successful signatureverification.

A duplicate document command produces a printed copy of thecorresponding document instance with background field values preserved.If the document contains any forms, then the duplicate document commandduplicates the forms in the same way a duplicate form command does. Areset document command produces a printed copy of the correspondingdocument instance with background field values discarded. If thedocument contains any forms, then the reset document command resets theforms in the same way a reset form command does. A get document statuscommand produces a printed report on the status of the correspondingdocument instance, including who published it, when it was printed, forwhom it was printed, and the status of any forms it contains.

If the page server command's “on selected” attribute is set, then thecommand operates on the page identified by the pen's current selectionrather than on the page containing the command. This allows a menu ofpage server commands to be printed. If the target page doesn't contain apage server command element for the designated page server command, thenthe command is ignored.

An application can provide application-specific handling by embeddingthe relevant page server command element in a hyperlinked group. Thepage server activates the hyperlink associated with the hyperlinkedgroup rather than executing the page server command.

A page server command element is hidden if its “hidden” attribute isset. A hidden command element does not have an input zone on a page andso cannot be activated directly by a user. It can, however, be activatedvia a page server command embedded in a different page, if that pageserver command has its “on selected” attribute set.

1.8 Standard Features of Netpages

In the preferred form, each netpage is printed with the netpage logo atthe bottom to indicate that it is a netpage and therefore hasinteractive properties. The logo also acts as a copy button. In mostcases pressing the logo produces a copy of the page. In the case of aform, the button produces a copy of the entire form. And in the case ofa secure document, such as a ticket or coupon, the button elicits anexplanatory note or advertising page.

The default single-page copy function is handled directly by therelevant netpage page server. Special copy functions are handled bylinking the logo button to an application.

1.9 User Help System

In a preferred embodiment, the netpage printer has a single buttonlabelled “Help”. When pressed it elicits a single help page 46 ofinformation, including:

status of printer connection

status of printer consumables

top-level help menu

document function menu

top-level netpage network directory

The help menu provides a hierarchical manual on how to use the netpagesystem.

The document function menu includes the following functions:

print a copy of a document

print a clean copy of a form

print the status of a document

A document function is initiated by selecting the document and thenpressing the button. The status of a document indicates who published itand when, to whom it was delivered, and to whom and when it wassubsequently submitted as a form.

The help page is obviously unavailable if the printer is unable toprint. In this case the “error” light is lit and the user can requestremote diagnosis over the network.

2 Personalized Publication Model

In the following description, news is used as a canonical publicationexample to illustrate personalization mechanisms in the netpage system.Although news is often used in the limited sense of newspaper andnewsmagazine news, the intended scope in the present context is wider.

In the netpage system, the editorial content and the advertising contentof a news publication are personalized using different mechanisms. Theeditorial content is personalized according to the reader's explicitlystated and implicitly captured interest profile. The advertising contentis personalized according to the reader's locality and demographic.

2.1 Editorial Personalization

A subscriber can draw on two kinds of news sources: those that delivernews publications, and those that deliver news streams. While newspublications are aggregated and edited by the publisher, news streamsare aggregated either by a news publisher or by a specialized newsaggregator. News publications typically correspond to traditionalnewspapers and newsmagazines, while news streams can be many and varied:a “raw” news feed from a news service, a cartoon strip, a freelancewriter's column, a friend's bulletin board, or the reader's own e-mail.

The netpage publication server supports the publication of edited newspublications as well as the aggregation of multiple news streams. Byhandling the aggregation and hence the formatting of news streamsselected directly by the reader, the server is able to place advertisingon pages over which it otherwise has no editorial control.

The subscriber builds a daily newspaper by selecting one or morecontributing news publications, and creating a personalized version ofeach. The resulting daily editions are printed and bound together into asingle newspaper. The various members of a household typically expresstheir different interests and tastes by selecting different dailypublications and then customizing them.

For each publication, the reader optionally selects specific sections.Some sections appear daily, while others appear weekly. The dailysections available from The New York Times online, for example, include“Page One Plus”, “National”, “International”, “Opinion”, “Business”,“Arts/Living”, “Technology”, and “Sports”. The set of available sectionsis specific to a publication, as is the default subset.

The reader can extend the daily newspaper by creating custom sections,each one drawing on any number of news streams. Custom sections might becreated for e-mail and friends' announcements (“Personal”), or formonitoring news feeds for specific topics (“Alerts” or “Clippings”).

For each section, the reader optionally specifies its size, eitherqualitatively (e.g. short, medium, or long), or numerically (i.e. as alimit on its number of pages), and the desired proportion ofadvertising, either qualitatively (e.g. high, normal, low, none), ornumerically (i.e. as a percentage).

The reader also optionally expresses a preference for a large number ofshorter articles or a small number of longer articles. Each article isideally written (or edited) in both short and long forms to support thispreference.

An article may also be written (or edited) in different versions tomatch the expected sophistication of the reader, for example to providechildren's and adults' versions. The appropriate version is selectedaccording to the reader's age. The reader can specify a “reading age”which takes precedence over their biological age.

The articles which make up each section are selected and prioritized bythe editors, and each is assigned a useful lifetime. By default they aredelivered to all relevant subscribers, in priority order, subject tospace constraints in the subscribers' editions.

In sections where it is appropriate, the reader may optionally enablecollaborative filtering. This is then applied to articles which have asufficiently long lifetime. Each article which qualifies forcollaborative filtering is printed with rating buttons at the end of thearticle. The buttons can provide an easy choice (e.g. “liked” and“disliked’), making it more likely that readers will bother to rate thearticle.

Articles with high priorities and short lifetimes are thereforeeffectively considered essential reading by the editors and aredelivered to most relevant subscribers.

The reader optionally specifies a serendipity factor, eitherqualitatively (e.g. do or don't surprise me), or numerically. A highserendipity factor lowers the threshold used for matching duringcollaborative filtering. A high factor makes it more likely that thecorresponding section will be filled to the reader's specified capacity.A different serendipity factor can be specified for different days ofthe week.

The reader also optionally specifies topics of particular interestwithin a section, and this modifies the priorities assigned by theeditors.

The speed of the reader's Internet connection affects the quality atwhich images can be delivered. The reader optionally specifies apreference for fewer images or smaller images or both. If the number orsize of images is not reduced, then images may be delivered at lowerquality (i.e. at lower resolution or with greater compression).

At a global level, the reader specifies how quantities, dates, times andmonetary values are localized. This involves specifying whether unitsare imperial or metric, a local timezone and time format, and a localcurrency, and whether the localization consist of in situ translation orannotation. These preferences are derived from the reader's locality bydefault.

To reduce reading difficulties caused by poor eyesight, the readeroptionally specifies a global preference for a larger presentation. Bothtext and images are scaled accordingly, and less information isaccommodated on each page.

The language in which a news publication is published, and itscorresponding text encoding, is a property of the publication and not apreference expressed by the user. However, the netpage system can beconfigured to provide automatic translation services in various guises.

2.2 Advertising Localization and Targeting

The personalization of the editorial content directly affects theadvertising content, because advertising is typically placed to exploitthe editorial context. Travel ads, for example, are more likely toappear in a travel section than elsewhere. The value of the editorialcontent to an advertiser (and therefore to the publisher) lies in itsability to attract large numbers of readers with the right demographics.

Effective advertising is placed on the basis of locality anddemographics. Locality determines proximity to particular services,retailers etc., and particular interests and concerns associated withthe local community and environment. Demographics determine generalinterests and preoccupations as well as likely spending patterns.

A news publisher's most profitable product is advertising “space”, amulti-dimensional entity determined by the publication's geographiccoverage, the size of its readership, its readership demographics, andthe page area available for advertising.

In the netpage system, the netpage publication server computes theapproximate multi-dimensional size of a publication's saleableadvertising space on a per-section basis, taking into account thepublication's geographic coverage, the section's readership, the size ofeach reader's section edition, each reader's advertising proportion, andeach reader's demographic.

In comparison with other media, the netpage system allows theadvertising space to be defined in greater detail, and allows smallerpieces of it to be sold separately. It therefore allows it to be sold atcloser to its true value.

For example, the same advertising “slot” can be sold in varyingproportions to several advertisers, with individual readers' pagesrandomly receiving the advertisement of one advertiser or another,overall preserving the proportion of space sold to each advertiser.

The netpage system allows advertising to be linked directly to detailedproduct information and online purchasing. It therefore raises theintrinsic value of the advertising space.

Because personalization and localization are handled automatically bynetpage publication servers, an advertising aggregator can providearbitrarily broad coverage of both geography and demographics. Thesubsequent disaggregation is efficient because it is automatic. Thismakes it more cost-effective for publishers to deal with advertisingaggregators than to directly capture advertising. Even though theadvertising aggregator is taking a proportion of advertising revenue,publishers may find the change profit-neutral because of the greaterefficiency of aggregation. The advertising aggregator acts as anintermediary between advertisers and publishers, and may place the sameadvertisement in multiple publications.

It is worth noting that ad placement in a netpage publication can bemore complex than ad placement in the publication's traditionalcounterpart, because the publication's advertising space is morecomplex. While ignoring the full complexities of negotiations betweenadvertisers, advertising aggregators and publishers, the preferred formof the netpage system provides some automated support for thesenegotiations, including support for automated auctions of advertisingspace. Automation is particularly desirable for the placement ofadvertisements which generate small amounts of income, such as small orhighly localized advertisements.

Once placement has been negotiated, the aggregator captures and editsthe advertisement and records it on a netpage ad server.Correspondingly, the publisher records the ad placement on the relevantnetpage publication server. When the netpage publication server lays outeach user's personalized publication, it picks the relevantadvertisements from the netpage ad server.

2.3 User Profiles 2.3.1 Information Filtering

The personalization of news and other publications relies on anassortment of user-specific profile information, including:

publication customizations

collaborative filtering vectors

contact details

presentation preferences

The customization of a publication is typically publication-specific,and so the customization information is maintained by the relevantnetpage publication server.

A collaborative filtering vector consists of the user's ratings of anumber of news items. It is used to correlate different users' interestsfor the purposes of making recommendations. Although there are benefitsto maintaining a single collaborative filtering vector independently ofany particular publication, there are two reasons why it is morepractical to maintain a separate vector for each publication: there islikely to be more overlap between the vectors of subscribers to the samepublication than between those of subscribers to different publications;and a publication is likely to want to present its users' collaborativefiltering vectors as part of the value of its brand, not to be foundelsewhere. Collaborative filtering vectors are therefore also maintainedby the relevant netpage publication server.

Contact details, including name, street address, ZIP Code, state,country, telephone numbers, are global by nature, and are maintained bya netpage registration server.

Presentation preferences, including those for quantities, dates andtimes, are likewise global and maintained in the same way.

The localization of advertising relies on the locality indicated in theuser's contact details, while the targeting of advertising relies onpersonal information such as date of birth, gender, marital status,income, profession, education, or qualitative derivatives such as agerange and income range.

For those users who choose to reveal personal information foradvertising purposes, the information is maintained by the relevantnetpage registration server. In the absence of such information,advertising can be targeted on the basis of the demographic associatedwith the user's ZIP or ZIP+4 Code.

Each user, pen, printer, application provider and application isassigned its own unique identifier, and the netpage registration servermaintains the relationships between them, as shown in FIGS. 21, 22, 23and 24. For registration purposes, a publisher is a special kind ofapplication provider, and a publication is a special kind ofapplication.

Each user 800 may be authorized to use any number of printers 802, andeach printer may allow any number of users to use it. Each user has asingle default printer (at 66), to which periodical publications aredelivered by default, whilst pages printed on demand are delivered tothe printer through which the user is interacting. The server keepstrack of which publishers a user has authorized to print to the user'sdefault printer. A publisher does not record the ID of any particularprinter, but instead resolves the ID when it is required. The user mayalso be designated as having administrative privileges 69 on theprinter, allowing the user to authorize other users to use the printer.This only has meaning if the printer requires administrative privileges84 for such operations.

When a user subscribes 808 to a publication 807, the publisher 806 (i.e.application provider 803) is authorized to print to a specified printeror the user's default printer. This authorization can be revoked at anytime by the user. Each user may have several pens 801, but a pen isspecific to a single user. If a user is authorized to use a particularprinter, then that printer recognizes any of the user's pens.

The pen ID is used to locate the corresponding user profile maintainedby a particular netpage registration server, via the DNS in the usualway.

A Web terminal 809 can be authorized to print on a particular netpageprinter, allowing Web pages and netpage documents encountered during Webbrowsing to be conveniently printed on the nearest netpage printer.

The netpage system can collect, on behalf of a printer provider, feesand commissions on income earned through publications printed on theprovider's printers. Such income can include advertising fees,click-through fees, e-commerce commissions, and transaction fees. If theprinter is owned by the user, then the user is the printer provider.

Each user also has a netpage account 820 which is used to accumulatemicro-debits and credits (such as those described in the precedingparagraph); contact details 815, including name, address and telephonenumbers; global preferences 816, including privacy, delivery andlocalization settings; any number of biometric records 817, containingthe user's encoded signature 818, fingerprint 819 etc; a handwritingmodel 819 automatically maintained by the system; and SET payment cardaccounts 821, with which e-commerce payments can be made.

In addition to the user-specific netpage account, each user also has anetpage account 936 specific to each printer the user is authorized touse. Each printer-specific account is used to accumulate micro-debitsand credits related to the user's activities on that printer. The useris billed on a regular basis for any outstanding debit balances.

A user optionally appears in the netpage user directory 823, allowingother users to locate and direct e-mail (etc.) to the user.

2.4 Intelligent Page Layout

The netpage publication server automatically lays out the pages of eachuser's personalized publication on a section-by-section basis. Sincemost advertisements are in the form of pre-formatted rectangles, theyare placed on the page before the editorial content.

The advertising ratio for a section can be achieved with wildly varyingadvertising ratios on individual pages within the section, and the adlayout algorithm exploits this. The algorithm is configured to attemptto co-locate closely tied editorial and advertising content, such asplacing ads for roofing material specifically within the publicationbecause of a special feature on do-it-yourself roofing repairs.

The editorial content selected for the user, including text andassociated images and graphics, is then laid out according to variousaesthetic rules.

The entire process, including the selection of ads and the selection ofeditorial content, must be iterated once the layout has converged, toattempt to more closely achieve the user's stated section sizepreference. The section size preference can, however, be matched onaverage over time, allowing significant day-to-day variations.

2.5 Document Format

Once the document is laid out, it is encoded for efficient distributionand persistent storage on the netpage network.

The primary efficiency mechanism is the separation of informationspecific to a single user's edition and information shared betweenmultiple users' editions. The specific information consists of the pagelayout. The shared information consists of the objects to which the pagelayout refers, including images, graphics, and pieces of text.

A text object contains fully-formatted text represented in theExtensible Markup Language (XML) using the Extensible StylesheetLanguage (XSL). XSL provides precise control over text formattingindependently of the region into which the text is being set, which inthis case is being provided by the layout. The text object containsembedded language codes to enable automatic translation, and embeddedhyphenation hints to aid with paragraph formatting.

An image object encodes an image in the JPEG 2000 wavelet-basedcompressed image format. A graphic object encodes a 2D graphic inScalable Vector Graphics (SVG) format.

The layout itself consists of a series of placed image and graphicobjects, linked textflow objects through which text objects flow,hyperlinks and input fields as described above, and watermark regions.These layout objects are summarized in Table 3. The layout uses acompact format suitable for efficient distribution and storage.

TABLE 3 netpage layout objects Layout object Attribute Format of linkedobject Image Position — Image object ID JPEG 2000 Graphic Position —Graphic object ID SVG Textflow Textflow ID — Zone — Optional text objectID XML/XSL Hyperlink Type — Zone — Application ID, etc. — Field Type —Meaning — Zone — Watermark Zone —

2.6 Document Distribution

As described above, for purposes of efficient distribution andpersistent storage on the netpage network, a user-specific page layoutis separated from the shared objects to which it refers.

When a subscribed publication is ready to be distributed, the netpagepublication server allocates, with the help of the netpage ID server 12,a unique ID for each page, page instance, document, and documentinstance.

The server computes a set of optimized subsets of the shared content andcreates a multicast channel for each subset, and then tags eachuser-specific layout with the names of the multicast channels which willcarry the shared content used by that layout. The server then pointcastseach user's layouts to that user's printer via the appropriate pageserver, and when the pointcasting is complete, multicasts the sharedcontent on the specified channels. After receiving its pointcast, eachpage server and printer subscribes to the multicast channels specifiedin the page layouts. During the multicasts, each page server and printerextracts from the multicast streams those objects referred to by itspage layouts. The page servers persistently archive the received pagelayouts and shared content.

Once a printer has received all the objects to which its page layoutsrefer, the printer re-creates the fully-populated layout and thenrasterizes and prints it.

Under normal circumstances, the printer prints pages faster than theycan be delivered. Assuming a quarter of each page is covered withimages, the average page has a size of less than 400 KB. The printer cantherefore hold in excess of 100 such pages in its internal 64 MB memory,allowing for temporary buffers etc. The printer prints at a rate of onepage per second. This is equivalent to 400 KB or about 3 Mbit of pagedata per second, which is similar to the highest expected rate of pagedata delivery over a broadband network.

Even under abnormal circumstances, such as when the printer runs out ofpaper, it is likely that the user will be able to replenish the papersupply before the printer'100-page internal storage capacity isexhausted.

However, if the printer's internal memory does fill up, then the printerwill be unable to make use of a multicast when it first occurs. Thenetpage publication server therefore allows printers to submit requestsfor re-multicasts. When a critical number of requests is received or atimeout occurs, the server re-multicasts the corresponding sharedobjects.

Once a document is printed, a printer can produce an exact duplicate atany time by retrieving its page layouts and contents from the relevantpage server.

2.7 On-Demand Documents

When a netpage document is requested on demand, it can be personalizedand delivered in much the same way as a periodical. However, since thereis no shared content, delivery is made directly to the requestingprinter without the use of multicast.

When a non-netpage document is requested on demand, it is notpersonalized, and it is delivered via a designated netpage formattingserver which reformats it as a netpage document. A netpage formattingserver is a special instance of a netpage publication server. Thenetpage formatting server has knowledge of various Internet documentformats, including Adobe's Portable Document Format (PDF), and HypertextMarkup Language (HTML). In the case of HTML, it can make use of thehigher resolution of the printed page to present Web pages in amulti-column format, with a table of contents. It can automaticallyinclude all Web pages directly linked to the requested page. The usercan tune this behavior via a preference.

The netpage formatting server makes standard netpage behavior, includinginteractivity and persistence, available on any Internet document, nomatter what its origin and format. It hides knowledge of differentdocument formats from both the netpage printer and the netpage pageserver, and hides knowledge of the netpage system from Web servers.

3 Security 3.1 Cryptography

Cryptography is used to protect sensitive information, both in storageand in transit, and to authenticate parties to a transaction. There aretwo classes of cryptography in widespread use: secret-key cryptographyand public-key cryptography. The netpage network uses both classes ofcryptography.

Secret-key cryptography, also referred to as symmetric cryptography,uses the same key to encrypt and decrypt a message. Two parties wishingto exchange messages must first arrange to securely exchange the secretkey.

Public-key cryptography, also referred to as asymmetric cryptography,uses two encryption keys. The two keys are mathematically related insuch a way that any message encrypted using one key can only bedecrypted using the other key. One of these keys is then published,while the other is kept private. The public key is used to encrypt anymessage intended for the holder of the private key. Once encrypted usingthe public key, a message can only be decrypted using the private key.Thus two parties can securely exchange messages without first having toexchange a secret key. To ensure that the private key is secure, it isnormal for the holder of the private key to generate the key pair.

Public-key cryptography can be used to create a digital signature. Theholder of the private key can create a known hash of a message and thenencrypt the hash using the private key. Anyone can then verify that theencrypted hash constitutes the “signature” of the holder of the privatekey with respect to that particular message by decrypting the encryptedhash using the public key and verifying the hash against the message. Ifthe signature is appended to the message, then the recipient of themessage can verify both that the message is genuine and that it has notbeen altered in transit.

To make public-key cryptography work, there has to be a way todistribute public keys which prevents impersonation. This is normallydone using certificates and certificate authorities. A certificateauthority is a trusted third party which authenticates the connectionbetween a public key and someone's identity. The certificate authorityverifies the person's identity by examining identity documents, and thencreates and signs a digital certificate containing the person's identitydetails and public key. Anyone who trusts the certificate authority canuse the public key in the certificate with a high degree of certaintythat it is genuine. They just have to verify that the certificate hasindeed been signed by the certificate authority, whose public key iswell-known.

In most transaction environments, public-key cryptography is only usedto create digital signatures and to securely exchange secret sessionkeys. Secret-key cryptography is used for all other purposes.

In the following discussion, when reference is made to the securetransmission of information between a netpage printer and a server, whatactually happens is that the printer obtains the server's certificate,authenticates it with reference to the certificate authority, uses thepublic key-exchange key in the certificate to exchange a secret sessionkey with the server, and then uses the secret session key to encrypt themessage data. A session key, by definition, can have an arbitrarilyshort lifetime.

3.2 Netpage Printer Security

Each netpage printer is assigned a pair of unique identifiers at time ofmanufacture which are stored in read-only memory in the printer and inthe netpage registration server database. The first ID 62 is public anduniquely identifies the printer on the netpage network. The second ID issecret and is used when the printer is first registered on the network.

When the printer connects to the netpage network for the first timeafter installation, it creates a signature public/private key pair. Ittransmits the secret ID and the public key securely to the netpageregistration server. The server compares the secret ID against theprinter's secret ID recorded in its database, and accepts theregistration if the IDs match. It then creates and signs a certificatecontaining the printer's public ID and public signature key, and storesthe certificate in the registration database.

The netpage registration server acts as a certificate authority fornetpage printers, since it has access to secret information allowing itto verify printer identity.

When a user subscribes to a publication, a record is created in thenetpage registration server database authorizing the publisher to printthe publication to the user's default printer or a specified printer.Every document sent to a printer via a page server is addressed to aparticular user and is signed by the publisher using the publisher'sprivate signature key. The page server verifies, via the registrationdatabase, that the publisher is authorized to deliver the publication tothe specified user. The page server verifies the signature using thepublisher's public key, obtained from the publisher's certificate storedin the registration database.

The netpage registration server accepts requests to add printingauthorizations to the database, so long as those requests are initiatedvia a pen registered to the printer.

3.3 Netpage Pen Security

Each netpage pen is assigned a unique identifier at time of manufacturewhich is stored in read-only memory in the pen and in the netpageregistration server database. The pen ID 61 uniquely identifies the penon the netpage network.

A netpage pen can “know” a number of netpage printers, and a printer can“know” a number of pens. A pen communicates with a printer via a radiofrequency signal whenever it is within range of the printer. Once a penand printer are registered, they regularly exchange session keys.Whenever the pen transmits digital ink to the printer, the digital inkis always encrypted using the appropriate session key. Digital ink isnever transmitted in the clear.

A pen stores a session key for every printer it knows, indexed byprinter ID, and a printer stores a session key for every pen it knows,indexed by pen ID. Both have a large but finite storage capacity forsession keys, and will forget a session key on a least-recently-usedbasis if necessary.

When a pen comes within range of a printer, the pen and printer discoverwhether they know each other. If they don't know each other, then theprinter determines whether it is supposed to know the pen. This mightbe, for example, because the pen belongs to a user who is registered touse the printer. If the printer is meant to know the pen but doesn't,then it initiates the automatic pen registration procedure. If theprinter isn't meant to know the pen, then it agrees with the pen toignore it until the pen is placed in a charging cup, at which time itinitiates the registration procedure.

In addition to its public ID, the pen contains a secret key-exchangekey. The key-exchange key is also recorded in the netpage registrationserver database at time of manufacture. During registration, the pentransmits its pen ID to the printer, and the printer transmits the penID to the netpage registration server. The server generates a sessionkey for the printer and pen to use, and securely transmits the sessionkey to the printer. It also transmits a copy of the session keyencrypted with the pen's key-exchange key. The printer stores thesession key internally, indexed by the pen ID, and transmits theencrypted session key to the pen. The pen stores the session keyinternally, indexed by the printer ID.

Although a fake pen can impersonate a pen in the pen registrationprotocol, only a real pen can decrypt the session key transmitted by theprinter.

When a previously unregistered pen is first registered, it is of limiteduse until it is linked to a user. A registered but “un-owned” pen isonly allowed to be used to request and fill in netpage user and penregistration forms, to register a new user to which the new pen isautomatically linked, or to add a new pen to an existing user.

The pen uses secret-key rather than public-key encryption because ofhardware performance constraints in the pen.

3.4 Secure Documents

The netpage system supports the delivery of secure documents such astickets and coupons. The netpage printer includes a facility to printwatermarks, but will only do so on request from publishers who aresuitably authorized. The publisher indicates its authority to printwatermarks in its certificate, which the printer is able toauthenticate.

The “watermark” printing process uses an alternative dither matrix inspecified “watermark” regions of the page. Back-to-back pages containmirror-image watermark regions which coincide when printed. The dithermatrices used in odd and even pages' watermark regions are designed toproduce an interference effect when the regions are viewed together,achieved by looking through the printed sheet.

The effect is similar to a watermark in that it is not visible whenlooking at only one side of the page, and is lost when the page iscopied by normal means.

Pages of secure documents cannot be copied using the built-in netpagecopy mechanism described in Section 1.9 above. This extends to copyingnetpages on netpage-aware photocopiers.

Secure documents are typically generated as part of e-commercetransactions. They can therefore include the user's photograph which wascaptured when the user registered biometric information with the netpageregistration server, as described in Section 2.

When presented with a secure netpage document, the recipient can verifyits authenticity by requesting its status in the usual way. The uniqueID of a secure document is only valid for the lifetime of the document,and secure document IDs are allocated non-contiguously to prevent theirprediction by opportunistic forgers. A secure document verification pencan be developed with built-in feedback on verification failure, tosupport easy point-of-presentation document verification.

Clearly neither the watermark nor the user's photograph are secure in acryptographic sense. They simply provide a significant obstacle tocasual forgery. Online document verification, particularly using averification pen, provides an added level of security where it isneeded, but is still not entirely immune to forgeries.

3.5 Non-Repudiation

In the netpage system, forms submitted by users are delivered reliablyto forms handlers and are persistently archived on netpage page servers.It is therefore impossible for recipients to repudiate delivery.

E-commerce payments made through the system, as described in Section 4,are also impossible for the payee to repudiate.

4 Electronic Commerce Model 4.1 Secure Electronic Transaction (Set)

The netpage system uses the Secure Electronic Transaction (SET) systemas one of its payment systems. SET, having been developed by MasterCardand Visa, is organized around payment cards, and this is reflected inthe terminology. However, much of the system is independent of the typeof accounts being used.

In SET, cardholders and merchants register with a certificate authorityand are issued with certificates containing their public signature keys.The certificate authority verifies a cardholder's registration detailswith the card issuer as appropriate, and verifies a merchant'sregistration details with the acquirer as appropriate. Cardholders andmerchants store their respective private signature keys securely ontheir computers. During the payment process, these certificates are usedto mutually authenticate a merchant and cardholder, and to authenticatethem both to the payment gateway.

SET has not yet been adopted widely, partly because cardholdermaintenance of keys and certificates is considered burdensome. Interimsolutions which maintain cardholder keys and certificates on a serverand give the cardholder access via a password have met with somesuccess.

4.2 SET Payments

In the netpage system the netpage registration server acts as a proxyfor the netpage user (i.e. the cardholder) in SET payment transactions.

The netpage system uses biometrics to authenticate the user andauthorize SET payments. Because the system is pen-based, the biometricused is the user's on-line signature, consisting of time-varying penposition and pressure. A fingerprint biometric can also be used bydesigning a fingerprint sensor into the pen, although at a higher cost.The type of biometric used only affects the capture of the biometric,not the authorization aspects of the system.

The first step to being able to make SET payments is to register theuser's biometric with the netpage registration server. This is done in acontrolled environment, for example a bank, where the biometric can becaptured at the same time as the user's identity is verified. Thebiometric is captured and stored in the registration database, linked tothe user's record. The user's photograph is also optionally captured andlinked to the record. The SET cardholder registration process iscompleted, and the resulting private signature key and certificate arestored in the database. The user's payment card information is alsostored, giving the netpage registration server enough information to actas the user's proxy in any SET payment transaction.

When the user eventually supplies the biometric to complete a payment,for example by signing a netpage order form, the printer securelytransmits the order information, the pen ID and the biometric data tothe netpage registration server. The server verifies the biometric withrespect to the user identified by the pen ID, and from then on acts asthe user's proxy in completing the SET payment transaction.

4.3 Micro-Payments

The netpage system includes a mechanism for micro-payments, to allow theuser to be conveniently charged for printing low-cost documents ondemand and for copying copyright documents, and possibly also to allowthe user to be reimbursed for expenses incurred in printing advertisingmaterial. The latter depends on the level of subsidy already provided tothe user.

When the user registers for e-commerce, a network account is establishedwhich aggregates micro-payments. The user receives a statement on aregular basis, and can settle any outstanding debit balance using thestandard payment mechanism.

The network account can be extended to aggregate subscription fees forperiodicals, which would also otherwise be presented to the user in theform of individual statements.

4.4 Transactions

When a user requests a netpage in a particular application context, theapplication is able to embed a user-specific transaction ID 55 in thepage. Subsequent input through the page is tagged with the transactionID, and the application is thereby able to establish an appropriatecontext for the user's input.

When input occurs through a page which is not user-specific, however,the application must use the user's unique identity to establish acontext. A typical example involves adding items from a pre-printedcatalog page to the user's virtual “shopping cart”. To protect theuser's privacy, however, the unique user ID 60 known to the netpagesystem is not divulged to applications. This is to prevent differentapplication providers from easily correlating independently accumulatedbehavioral data.

The netpage registration server instead maintains an anonymousrelationship between a user and an application via a unique alias ID 65,as shown in FIG. 24. Whenever the user activates a hyperlink tagged withthe “registered” attribute, the netpage page server asks the netpageregistration server to translate the associated application ID 64,together with the pen ID 61, into an alias ID 65. The alias ID is thensubmitted to the hyperlink's application.

The application maintains state information indexed by alias ID, and isable to retrieve user-specific state information without knowledge ofthe global identity of the user.

The system also maintains an independent certificate and privatesignature key for each of a user's applications, to allow it to signapplication transactions on behalf of the user using onlyapplication-specific information.

To assist the system in routing product bar code (UPC) “hyperlink”activations, the system records a favorite application on behalf of theuser for any number of product types.

Each application is associated with an application provider, and thesystem maintains an account on behalf of each application provider, toallow it to credit and debit the provider for click-through fees etc.

An application provider can be a publisher of periodical subscribedcontent. The system records the user's willingness to receive thesubscribed publication, as well as the expected frequency ofpublication.

Communications Protocols

A communications protocol defines an ordered exchange of messagesbetween entities. In the netpage system, entities such as pens, printersand servers utilise a set of defined protocols to cooperatively handleuser interaction with the netpage system.

Each protocol is illustrated by way of a sequence diagram in which thehorizontal dimension is used to represent message flow and the verticaldimension is used to represent time. Each entity is represented by arectangle containing the name of the entity and a vertical columnrepresenting the lifeline of the entity. During the time an entityexists, the lifeline is shown as a dashed line. During the time anentity is active, the lifeline is shown as a double line. Because theprotocols considered here do not create or destroy entities, lifelinesare generally cut short as soon as an entity ceases to participate in aprotocol.

5.1 Subscription Delivery Protocol

A preferred embodiment of a subscription delivery protocol is shown inFIG. 40.

A large number of users may subscribe to a periodical publication. Eachuser's edition may be laid out differently, but many users' editionswill share common content such as text objects and image objects. Thesubscription delivery protocol therefore delivers document structures toindividual printers via pointcast, but delivers shared content objectsvia multicast.

The application (i.e. publisher) first obtains a document ID 51 for eachdocument from an ID server 12. It then sends each document structure,including its document ID and page descriptions, to the page server 10responsible for the document's newly allocated ID. It includes its ownapplication ID 64, the subscriber's alias ID 65, and the relevant set ofmulticast channel names. It signs the message using its privatesignature key.

The page server uses the application ID and alias ID to obtain from theregistration server the corresponding user ID 60, the user's selectedprinter ID 62 (which may be explicitly selected for the application, ormay be the user's default printer), and the application's certificate.

The application's certificate allows the page server to verify themessage signature. The page server's request to the registration serverfails if the application ID and alias ID don't together identify asubscription 808.

The page server then allocates document and page instance IDs andforwards the page descriptions, including page IDs 50, to the printer.It includes the relevant set of multicast channel names for the printerto listen to.

It then returns the newly allocated page IDs to the application forfuture reference.

Once the application has distributed all of the document structures tothe subscribers' selected printers via the relevant page servers, itmulticasts the various subsets of the shared objects on the previouslyselected multicast channels. Both page servers and printers monitor theappropriate multicast channels and receive their required contentobjects. They are then able to populate the previously pointcastdocument structures. This allows the page servers to add completedocuments to their databases, and it allows the printers to print thedocuments.

5.2 Hyperlink Activation Protocol

A preferred embodiment of a hyperlink activation protocol is shown inFIG. 42.

When a user clicks on a netpage with a netpage pen, the pen communicatesthe click to the nearest netpage printer 601. The click identifies thepage and a location on the page. The printer already knows the ID 61 ofthe pen from the pen connection protocol.

The printer determines, via the DNS, the network address of the pageserver 10 a handling the particular page ID 50. The address may alreadybe in its cache if the user has recently interacted with the same page.The printer then forwards the pen ID, its own printer ID 62, the page IDand click location to the page server.

The page server loads the page description 5 identified by the page IDand determines which input element's zone 58, if any, the click lies in.Assuming the relevant input element is a hyperlink element 844, the pageserver then obtains the associated application ID 64 and link ID 54, anddetermines, via the DNS, the network address of the application serverhosting the application 71.

The page server uses the pen ID 61 to obtain the corresponding user ID60 from the registration server 11, and then allocates a globally uniquehyperlink request ID 52 and builds a hyperlink request 934. Thehyperlink request class diagram is shown in FIG. 41. The hyperlinkrequest records the IDs of the requesting user and printer, andidentifies the clicked hyperlink instance 862. The page server thensends its own server ID 53, the hyperlink request ID, and the link ID tothe application.

The application produces a response document according toapplication-specific logic, and obtains a document ID 51 from an IDserver 12. It then sends the document to the page server 10 bresponsible for the document's newly allocated ID, together with therequesting page server's ID and the hyperlink request ID.

The second page server sends the hyperlink request ID and application IDto the first page server to obtain the corresponding user ID and printerID 62. The first page server rejects the request if the hyperlinkrequest has expired or is for a different application.

The second page server allocates document instance and page IDs 50,returns the newly allocated page IDs to the application, adds thecomplete document to its own database, and finally sends the pagedescriptions to the requesting printer.

The hyperlink instance may include a meaningful transaction ID 55, inwhich case the first page server includes the transaction ID in themessage sent to the application. This allows the application toestablish a transaction-specific context for the hyperlink activation.

If the hyperlink requires a user alias, i.e. its “alias required”attribute is set, then the first page server sends both the pen ID 61and the hyperlink's application ID 64 to the registration server 11 toobtain not just the user ID corresponding to the pen ID but also thealias ID 65 corresponding to the application ID and the user ID. Itincludes the alias ID in the message sent to the application, allowingthe application to establish a user-specific context for the hyperlinkactivation.

5.3 Handwriting Recognition Protocol

When a user draws a stroke on a netpage with a netpage pen, the pencommunicates the stroke to the nearest netpage printer. The strokeidentifies the page and a path on the page.

The printer forwards the pen ID 61, its own printer ID 62, the page ID50 and stroke path to the page server 10 in the usual way.

The page server loads the page description 5 identified by the page IDand determines which input element's zone 58, if any, the strokeintersects. Assuming the relevant input element is a text field 878, thepage server appends the stroke to the text field's digital ink.

After a period of inactivity in the zone of the text field, the pageserver sends the pen ID and the pending strokes to the registrationserver 11 for interpretation. The registration server identifies theuser corresponding to the pen, and uses the user's accumulatedhandwriting model 822 to interpret the strokes as handwritten text. Onceit has converted the strokes to text, the registration server returnsthe text to the requesting page server. The page server appends the textto the text value of the text field.

5.4 Signature Verification Protocol

Assuming the input element whose zone the stroke intersects is asignature field 880, the page server 10 appends the stroke to thesignature field's digital ink.

After a period of inactivity in the zone of the signature field, thepage server sends the pen ID 61 and the pending strokes to theregistration server 11 for verification. It also sends the applicationID 64 associated with the form of which the signature field is part, aswell as the form ID 56 and the current data content of the form. Theregistration server identifies the user corresponding to the pen, anduses the user's dynamic signature biometric 818 to verify the strokes asthe user's signature. Once it has verified the signature, theregistration server uses the application ID 64 and user ID 60 toidentify the user's application-specific private signature key. It thenuses the key to generate a digital signature of the form data, andreturns the digital signature to the requesting page server. The pageserver assigns the digital signature to the signature field and sets theassociated form's status to frozen.

The digital signature includes the alias ID 65 of the correspondinguser. This allows a single form to capture multiple users' signatures.

5.5 Form Submission Protocol

A preferred embodiment of a form submission protocol is shown in FIG.43.

Form submission occurs via a form hyperlink activation. It thus followsthe protocol defined in Section 5.2, with some form-specific additions.

In the case of a form hyperlink, the hyperlink activation message sentby the page server 10 to the application 71 also contains the form ID 56and the current data content of the form. If the form contains anysignature fields, then the application verifies each one by extractingthe alias ID 65 associated with the corresponding digital signature andobtaining the corresponding certificate from the registration server 11.

6 Netpage Pen Description 6.1 Pen Mechanics

Referring to FIGS. 8 and 9, the pen, generally designated by referencenumeral 101, includes a housing 102 in the form of a plastics mouldinghaving walls 103 defining an interior space 104 for mounting the pencomponents. The pen top 105 is in operation rotatably mounted at one end106 of the housing 102. A semi-transparent cover 107 is secured to theopposite end 108 of the housing 102. The cover 107 is also of mouldedplastics, and is formed from semi-transparent material in order toenable the user to view the status of the LED mounted within the housing102. The cover 107 includes a main part 109 which substantiallysurrounds the end 108 of the housing 102 and a projecting portion 110which projects back from the main part 109 and fits within acorresponding slot 111 formed in the walls 103 of the housing 102. Aradio antenna 112 is mounted behind the projecting portion 110, withinthe housing 102. Screw threads 113 surrounding an aperture 113A on thecover 107 are arranged to receive a metal end piece 114, includingcorresponding screw threads 115. The metal end piece 114 is removable toenable ink cartridge replacement.

Also mounted within the cover 107 is a tri-color status LED 116 on aflex PCB 117. The antenna 112 is also mounted on the flex PCB 117. Thestatus LED 116 is mounted at the top of the pen 101 for good all-aroundvisibility.

The pen can operate both as a normal marking ink pen and as anon-marking stylus. An ink pen cartridge 118 with nib 119 and a stylus120 with stylus nib 121 are mounted side by side within the housing 102.Either the ink cartridge nib 119 or the stylus nib 121 can be broughtforward through open end 122 of the metal end piece 114, by rotation ofthe pen top 105. Respective slider blocks 123 and 124 are mounted to theink cartridge 118 and stylus 120, respectively. A rotatable cam barrel125 is secured to the pen top 105 in operation and arranged to rotatetherewith. The cam barrel 125 includes a cam 126 in the form of a slotwithin the walls 181 of the cam barrel. Cam followers 127 and 128projecting from slider blocks 123 and 124 fit within the cam slot 126.On rotation of the cam barrel 125, the slider blocks 123 or 124 moverelative to each other to project either the pen nib 119 or stylus nib121 out through the hole 122 in the metal end piece 114. The pen 101 hasthree states of operation. By turning the top 105 through 90° steps, thethree states are:

Stylus 120 nib 121 out;

Ink cartridge 118 nib 119 out; and

Neither ink cartridge 118 nib 119 out nor stylus 120 nib 121 out.

A second flex PCB 129, is mounted on an electronics chassis 130 whichsits within the housing 102. The second flex PCB 129 mounts an infraredLED 131 for providing infrared radiation for projection onto thesurface. An image sensor 132 is provided mounted on the second flex PCB129 for receiving reflected radiation from the surface. The second flexPCB 129 also mounts a radio frequency chip 133, which includes an RFtransmitter and RF receiver, and a controller chip 134 for controllingoperation of the pen 101. An optics block 135 (formed from moulded clearplastics) sits within the cover 107 and projects an infrared beam ontothe surface and receives images onto the image sensor 132. Power supplywires 136 connect the components on the second flex PCB 129 to batterycontacts 137 which are mounted within the cam barrel 125. A terminal 138connects to the battery contacts 137 and the cam barrel 125. A threevolt rechargeable battery 139 sits within the cam barrel 125 in contactwith the battery contacts. An induction charging coil 140 is mountedabout the second flex PCB 129 to enable recharging of the battery 139via induction. The second flex PCB 129 also mounts an infrared LED 143and infrared photodiode 144 for detecting displacement in the cam barrel125 when either the stylus 120 or the ink cartridge 118 is used forwriting, in order to enable a determination of the force being appliedto the surface by the pen nib 119 or stylus nib 121. The IR photodiode144 detects light from the IR LED 143 via reflectors (not shown) mountedon the slider blocks 123 and 124.

Rubber grip pads 141 and 142 are provided towards the end 108 of thehousing 102 to assist gripping the pen 101, and top 105 also includes aclip 142 for clipping the pen 101 to a pocket.

6.2 Pen Controller

The pen 101 is arranged to determine the position of its nib (stylus nib121 or ink cartridge nib 119) by imaging, in the infrared spectrum, anarea of the surface in the vicinity of the nib. It records the locationdata from the nearest location tag, and is arranged to calculate thedistance of the nib 121 or 119 from the location tab utilising optics135 and controller chip 134. The controller chip 134 calculates theorientation of the pen and the nib-to-tag distance from the perspectivedistortion observed on the imaged tag.

Utilising the RF chip 133 and antenna 112 the pen 101 can transmit thedigital ink data (which is encrypted for security and packaged forefficient transmission) to the computing system.

When the pen is in range of a receiver, the digital ink data istransmitted as it is formed. When the pen 101 moves out of range,digital ink data is buffered within the pen 101 (the pen 101 circuitryincludes a buffer arranged to store digital ink data for approximately12 minutes of the pen motion on the surface) and can be transmittedlater.

The controller chip 134 is mounted on the second flex PCB 129 in the pen101. FIG. 10 is a block diagram illustrating in more detail thearchitecture of the controller chip 134. FIG. 10 also showsrepresentations of the RF chip 133, the image sensor 132, the tri-colorstatus LED 116, the IR illumination LED 131, the IR force sensor LED143, and the force sensor photodiode 144.

The pen controller chip 134 includes a controlling processor 145. Bus146 enables the exchange of data between components of the controllerchip 134. Flash memory 147 and a 512 KB DRAM 148 are also included. Ananalog-to-digital converter 149 is arranged to convert the analog signalfrom the force sensor photodiode 144 to a digital signal.

An image sensor interface 152 interfaces with the image sensor 132. Atransceiver controller 153 and base band circuit 154 are also includedto interface with the RF chip 133 which includes an RF circuit 155 andRF resonators and inductors 156 connected to the antenna 112.

The controlling processor 145 captures and decodes location data fromtags from the surface via the image sensor 132, monitors the forcesensor photodiode 144, controls the LEDs 116, 131 and 143, and handlesshort-range radio communication via the radio transceiver 153. It is amedium-performance (˜40 MHz) general-purpose RISC processor.

The processor 145, digital transceiver components (transceivercontroller 153 and baseband circuit 154), image sensor interface 152,flash memory 147 and 512 KB DRAM 148 are integrated in a singlecontroller ASIC. Analog RF components (RF circuit 155 and RF resonatorsand inductors 156) are provided in the separate RF chip.

The image sensor is a 215×215 pixel CCD (such a sensor is produced byMatsushita Electronic Corporation, and is described in a paper byItakura, K T Nobusada, N Okusenyai, R Nagayoshi, and M Ozaki, “A 1 mm 50k-Pixel IT CCD Image Sensor for Miniature Camera System”, IEEETransactions on Electronic Devices, Volt 47, number 1, January 2000,which is incorporated herein by reference) with an IR filter.

The controller ASIC 134 enters a quiescent state after a period ofinactivity when the pen 101 is not in contact with a surface. Itincorporates a dedicated circuit 150 which monitors the force sensorphotodiode 144 and wakes up the controller 134 via the power manager 151on a pen-down event.

The radio transceiver communicates in the unlicensed 900 MHz bandnormally used by cordless telephones, or alternatively in the unlicensed2.4 GHz industrial, scientific and medical (ISM) band, and usesfrequency hopping and collision detection to provide interference-freecommunication.

In an alternative embodiment, the pen incorporates an Infrared DataAssociation (IrDA) interface for short-range communication with a basestation or netpage printer.

In a further embodiment, the pen 101 includes a pair of orthogonalaccelerometers mounted in the normal plane of the pen 101 axis. Theaccelerometers 190 are shown in FIGS. 9 and 10 in ghost outline.

The provision of the accelerometers enables this embodiment of the pen101 to sense motion without reference to surface location tags, allowingthe location tags to be sampled at a lower rate. Each location tag IDcan then identify an object of interest rather than a position on thesurface. For example, if the object is a user interface input element(e.g. a command button), then the tag ID of each location tag within thearea of the input element can directly identify the input element.

The acceleration measured by the accelerometers in each of the x and ydirections is integrated with respect to time to produce aninstantaneous velocity and position.

Since the starting position of the stroke is not known, only relativepositions within a stroke are calculated. Although position integrationaccumulates errors in the sensed acceleration, accelerometers typicallyhave high resolution, and the time duration of a stroke, over whicherrors accumulate, is short.

7 Netpage Printer Description 7.1 Printer Mechanics

The vertically-mounted netpage wallprinter 601 is shown fully assembledin FIG. 11. It prints netpages on Letter/A4 sized media using duplexed8½″ Memjet™ print engines 602 and 603, as shown in FIGS. 12 and 12A. Ituses a straight paper path with the paper 604 passing through theduplexed print engines 602 and 603 which print both sides of a sheetsimultaneously, in full color and with full bleed.

An integral binding assembly 605 applies a strip of glue along one edgeof each printed sheet, allowing it to adhere to the previous sheet whenpressed against it. This creates a final bound document 618 which canrange in thickness from one sheet to several hundred sheets.

The replaceable ink cartridge 627, shown in FIG. 13 coupled with theduplexed print engines, has bladders or chambers for storing fixative,adhesive, and cyan, magenta, yellow, black and infrared inks. Thecartridge also contains a micro air filter in a base molding. The microair filter interfaces with an air pump 638 inside the printer via a hose639. This provides filtered air to the printheads to prevent ingress ofmicro particles into the Memjet™ printheads 350 which might otherwiseclog the printhead nozzles. By incorporating the air filter within thecartridge, the operational life of the filter is effectively linked tothe life of the cartridge. The ink cartridge is a fully recyclableproduct with a capacity for printing and gluing 3000 pages (1500sheets).

Referring to FIG. 12, the motorized media pick-up roller assembly 626pushes the top sheet directly from the media tray past a paper sensor onthe first print engine 602 into the duplexed Memjet™ printhead assembly.The two Memjet™ print engines 602 and 603 are mounted in an opposingin-line sequential configuration along the straight paper path. Thepaper 604 is drawn into the first print engine 602 by integral, poweredpick-up rollers 626. The position and size of the paper 604 is sensedand full bleed printing commences. Fixative is printed simultaneously toaid drying in the shortest possible time.

The paper exits the first Memjet™ print engine 602 through a set ofpowered exit spike wheels (aligned along the straight paper path), whichact against a rubberized roller. These spike wheels contact the ‘wet’printed surface and continue to feed the sheet 604 into the secondMemjet™ print engine 603.

Referring to FIGS. 12 and 12A, the paper 604 passes from the duplexedprint engines 602 and 603 into the binder assembly 605. The printed pagepasses between a powered spike wheel axle 670 with a fibrous supportroller and another movable axle with spike wheels and a momentary actionglue wheel. The movable axle/glue assembly 673 is mounted to a metalsupport bracket and it is transported forward to interface with thepowered axle 670 via gears by action of a camshaft. A separate motorpowers this camshaft.

The glue wheel assembly 673 consists of a partially hollow axle 679 witha rotating coupling for the glue supply hose 641 from the ink cartridge627. This axle 679 connects to a glue wheel, which absorbs adhesive bycapillary action through radial holes. A molded housing 682 surroundsthe glue wheel, with an opening at the front. Pivoting side moldings andsprung outer doors are attached to the metal bracket and hinge outsideways when the rest of the assembly 673 is thrust forward. Thisaction exposes the glue wheel through the front of the molded housing682. Tension springs close the assembly and effectively cap the gluewheel during periods of inactivity.

As the sheet 604 passes into the glue wheel assembly 673, adhesive isapplied to one vertical edge on the front side (apart from the firstsheet of a document) as it is transported down into the binding assembly605.

7.2 Printer Controller Architecture

The netpage printer controller consists of a controlling processor 750,a factory-installed or field-installed network interface module 625, aradio transceiver (transceiver controller 753, baseband circuit 754, RFcircuit 755, and RF resonators and inductors 756), dual raster imageprocessor (RIP) DSPs 757, duplexed print engine controllers 760 a and760 b, flash memory 658, and 64 MB of DRAM 657, as illustrated in FIG.14.

The controlling processor handles communication with the network 19 andwith local wireless netpage pens 101, senses the help button 617,controls the user interface LEDs 613-616, and feeds and synchronizes theRIP DSPs 757 and print engine controllers 760. It consists of amedium-performance general-purpose microprocessor. The controllingprocessor 750 communicates with the print engine controllers 760 via ahigh-speed serial bus 659.

The RIP DSPs rasterize and compress page descriptions to the netpageprinter's compressed page format. Each print engine controller expands,dithers and prints page images to its associated Memjet™ printhead 350in real time (i.e. at over 30 pages per minute). The duplexed printengine controllers print both sides of a sheet simultaneously.

The master print engine controller 760 a controls the paper transportand monitors ink usage in conjunction with the master QA chip 665 andthe ink cartridge QA chip 761.

The printer controller's flash memory 658 holds the software for boththe processor 750 and the DSPs 757, as well as configuration data. Thisis copied to main memory 657 at boot time.

The processor 750, DSPs 757, and digital transceiver components(transceiver controller 753 and baseband circuit 754) are integrated ina single controller ASIC 656. Analog RF components (RF circuit 755 andRF resonators and inductors 756) are provided in a separate RF chip 762.The network interface module 625 is separate, since netpage printersallow the network connection to be factory-selected or field-selected.Flash memory 658 and the 2×256 Mbit (64 MB) DRAM 657 is also off-chip.The print engine controllers 760 are provided in separate ASICs.

A variety of network interface modules 625 are provided, each providinga netpage network interface 751 and optionally a local computer ornetwork interface 752. Netpage network Internet interfaces include POTSmodems, Hybrid Fiber-Coax (HFC) cable modems, ISDN modems, DSL modems,satellite transceivers, current and next-generation cellular telephonetransceivers, and wireless local loop (WLL) transceivers. Localinterfaces include IEEE 1284 (parallel port), 10Base-T and 100Base-TEthernet, USB and USB 2.0, IEEE 1394 (Firewire), and various emerginghome networking interfaces. If an Internet connection is available onthe local network, then the local network interface can be used as thenetpage network interface.

The radio transceiver 753 communicates in the unlicensed 900 MHz bandnormally used by cordless telephones, or alternatively in the unlicensed2.4 GHz industrial, scientific and medical (ISM) band, and usesfrequency hopping and collision detection to provide interference-freecommunication.

The printer controller optionally incorporates an Infrared DataAssociation (IrDA) interface for receiving data “squirted” from devicessuch as netpage cameras. In an alternative embodiment, the printer usesthe IrDA interface for short-range communication with suitablyconfigured netpage pens.

7.2.1 Rasterization and Printing

As shown in FIG. 77, once the main processor 750 has received (at 440)the document's page layouts and page objects into memory 657 (at 441),it runs the appropriate RIP software on the DSPs 757.

The DSPs 757 rasterize (at 442) each page description and compress (at443) the rasterized page image. The main processor stores eachcompressed page image in memory 657 (at 444). The simplest way toload-balance multiple DSPs is to let each DSP rasterize a separate page.The DSPs can always be kept busy since an arbitrary number of rasterizedpages can, in general, be stored in memory. This strategy only leads topotentially poor DSP utilization when rasterizing short documents.

Watermark regions in the page description are rasterized to acontone-resolution bi-level bitmap which is losslessly compressed tonegligible size and which forms part of the compressed page image.

The infrared (IR) layer of the printed page contains coded netpage tagsat a density of about six per inch. Each tag encodes the page ID, tagID, and control bits, and the data content of each tag is generatedduring rasterization and stored in the compressed page image.

The main processor 750 passes back-to-back page images to the duplexedprint engine controllers 760. Each print engine controller 760 storesthe compressed page image in its local memory 769, and starts the pageexpansion and printing pipeline. Page expansion and printing ispipelined because it is impractical to store an entire 114 MB bi-levelCMYK+IR page image in memory.

The print engine controller expands the compressed page image (at 445),dithers the expanded contone color data to bi-level dots (at 446),composites the expanded bi-level black layer over the dithered contonelayer (at 447), renders the expanded netpage tag data (at 448), andfinally prints the fully-rendered page (at 449) to produce a printednetpage 1.

7.2.2 Print Engine Controller

The page expansion and printing pipeline of the print engine controller760 consists of a high speed IEEE 1394 serial interface 659, a standardJPEG decoder 763, a standard Group 4 Fax decoder 764, a customhalftoner/compositor unit 765, a custom tag encoder 766, a lineloader/formatter unit 767, and a custom interface 768 to the Memjet™printhead 350.

The print engine controller 360 operates in a double buffered manner.While one page is loaded into DRAM 769 via the high speed serialinterface 659, the previously loaded page is read from DRAM 769 andpassed through the print engine controller pipeline. Once the page hasfinished printing, the page just loaded is printed while another page isloaded.

The first stage of the pipeline expands (at 763) the JPEG-compressedcontone CMYK layer, expands (at 764) the Group 4 Fax-compressed bi-levelblack layer, and renders (at 766) the bi-level netpage tag layeraccording to the tag format defined in section 1.2, all in parallel. Thesecond stage dithers (at 765) the contone CMYK layer and composites (at765) the bi-level black layer over the resulting bi-level CMYK layer.The resultant bi-level CMYK+IR dot data is buffered and formatted (at767) for printing on the Memjet™ printhead 350 via a set of linebuffers. Most of these line buffers are stored in the off-chip DRAM. Thefinal stage prints the six channels of bi-level dot data (includingfixative) to the Memjet™ printhead 350 via the printhead interface 768.

When several print engine controllers 760 are used in unison, such as ina duplexed configuration, they are synchronized via a shared line syncsignal 770. Only one print engine 760, selected via the externalmaster/slave pin 771, generates the line sync signal 770 onto the sharedline.

The print engine controller 760 contains a low-speed processor 772 forsynchronizing the page expansion and rendering pipeline, configuring theprinthead 350 via a low-speed serial bus 773, and controlling thestepper motors 675, 676.

In the 8½″ versions of the netpage printer, the two print engines eachprints 30 Letter pages per minute along the long dimension of the page(11″), giving a line rate of 8.8 kHz at 1600 dpi. In the 12″ versions ofthe netpage printer, the two print engines each prints 45 Letter pagesper minute along the short dimension of the page (8½″), giving a linerate of 10.2 kHz. These line rates are well within the operatingfrequency of the Memjet™ printhead, which in the current design exceeds30 kHz.

8 Netpage Photographs

Photographs taken with a digital camera can be printed as netpages. Auser can then obtain a pristine copy of a photo via the original print,even if the original print is severely degraded. The photo's digitalimage is persistently stored on the netpage network, and the printedphoto is a netpage linked to the digital image.

A user can archive and organize a collection of photos via a netpagephoto manager application. They can organize their photo collection intoa set of folders, delete unwanted photos from the collection, and searchfor photos in the collection.

A photo user can add photos to their netpage photo collection in severalways. They can take photos using a normal digital camera and “squirt”the photos to a receptive device which has access to the netpagenetwork. The squirting interface can be a radio interface (such asBluetooth) or an infrared interface (such as IrDA). The receptive devicecan be a mobile phone, a fixed or mobile netpage printer, etc.

They can also take and print photos using a netpage camera, i.e. adigital camera containing a netpage printer and a wireless netpagenetwork interface, as described in section 9 below. It typicallytransmits photos to the netpage network as they are taken. It can defertransmission until its local storage fills up, or until the userexplicitly requests transmission. The netpage system can pre-allocatepage IDs to netpage cameras on request, to allow them to print netpagephotos while off-line.

A photo user can grant other users (such as family members) access toparticular folders in their photo collection. Users can thus easilyshare photos without having to get together and swap negatives orprints. This may be particularly convenient when the photo user istravelling. Even if using a netpage camera, the photo user may choose todefer printing of photos while travelling, and instead retrieve andprint the photos on returning home, e.g. in the form of printed pagessuitable for inclusion in a normal photo album.

8.1 Application Drawing Notation

Each application user interface flow is illustrated as a collection ofdocuments linked by command arrows. A command arrow indicates that thetarget document is printed as a result of the user pressing thecorresponding command button on the source page. Some command arrows arelabelled with multiple commands separated by slashes (‘/’s), indicatingthat any one of the specified commands causes the target document to beprinted. Although multiple commands may label the same command arrow,they typically have different side-effects.

In application terms, it is important to distinguish between netpagedocuments and netpage forms. Documents contain printed information, aswell as command buttons which can be pressed by the user to requestfurther information or some other action. Forms, in addition to behavinglike normal documents, also contain input fields which can be filled inby the user. They provide the system with a data input mechanism. It isalso useful to distinguish between documents which contain genericinformation and documents which contain information specific to aparticular interaction between the user and an application. Genericdocuments may be pre-printed publications such as magazines sold at newsstands or advertising posters encountered in public places. Forms mayalso be pre-printed, including, for example, subscription formsencountered in pre-printed publications. They may, of course, also begenerated on-the-fly by a netpage printer in response to user requests.User-specific documents and forms are normally generated on the fly by anetpage printer in response to user requests. FIG. 44 shows a genericdocument 990, a generic form 991, a user-specific document 992, and auser-specific form 993.

Netpages which participate in a user interface flow are furtherdescribed by abstract page layouts. A page layout may contain variouskinds of elements, each of which has a unique style to differentiate itfrom the others. As shown in FIG. 45, these include fixed information994, variable information 995, input fields 996, command buttons 997,draggable commands 998, and text hyperlinks or hypertext links 999.

When a user interface flow is broken up into multiple diagrams, anydocument which is duplicated is shown with dashed outlines in all butthe main diagram which defines it.

8.2 Photo Collection Object Model

With reference to the photo collection class diagram shown in FIG. 46,the photo manager 400 manages photo collections on behalf of a number ofusers. Each photo user 402 is a netpage user 800 (FIG. 21), and thedetails of the photo user derive, by default, from the details of thecorresponding netpage user.

A netpage user may have any number of cameras 401, each of which has anID by which it identifies itself to the netpage system in much the sameway that a netpage pen does. A camera, like a pen, is associated withonly one netpage user, allowing the system to uniquely associate anyinput from a camera with a single user.

Each photo user has a collection 407 of photos, optionally organized 404into a set of named folders 405. Each folder has an optional access list403, indicating which other photo users are granted access to view thephotos in the folder.

With reference to the photo class diagram shown in FIG. 47, each photo408 in the photo collection has a caption, a capture date and time, anda capture location (e.g. if available from a GPS receiver in thecamera). Each photo has a photographer 415. Each photo has a full-sizeimage 417,413 and a corresponding thumbnail image 416,413. Each photorecords a set of camera settings 414, including focus, zoom, exposure,whether the flash was used, and the type and model of the camera. Actualcamera settings are camera-specific. A photo may have an associatedaudio annotation 411, if captured by the camera, and a text annotation410. If the photo was captured and printed by a camera which applied anartistic effect to the photo, then the artistic effect 409 is recordedso that the photo can be reproduced with or without the effect.

If the photo was squirted from a camera, then it is associated with asquirt group 412 which contains all the photos which were squirted as agroup. This provides a useful unit of organization when presenting thephoto collection to the user.

8.3 Photo Collection User Interface 8.3.1 Netpage Camera Photo Capture

When a user takes a photo using a netpage camera, the cameraautomatically transmits the photo to the netpage system. Since thecamera is uniquely associated with a particular netpage user, the photomanager automatically adds the photo to the user's photo collection. Asdescribed earlier, the camera may transmit the photo to the netpagesystem as soon as it is taken, or it may defer transmission until a moreopportune time.

8.3.2 Photo Squirting

When a user squirts a collection of photos to a netpage printer, theprinter sends the photos to the photo manager. If the camera is known tothe netpage system, then the camera manager adds the photos to thecorresponding user's photo collection. If the camera is not known, thenthe camera manager produces an Add Squirted Photos form 418 (FIG. 51)which allows the user to provide their identity by pressing the <addphotos> button. The page shows the first and last photo in the squirtgroup. The photo manager optionally requires the user to sign the formto allow their identity to be verified.

The photo squirting user interface flow is illustrated in FIG. 48.

8.3.3 Photo Browsing

The Photo Manager Menu form 420 (FIG. 52) provides a <photo history>button giving the user access to their photo collection presented bydate, and a <photo folders> button giving the user access to their photocollection via their named photo folders. The photo manager optionallyrequires the user to sign the form to allow their identity to beverified. The user obtains the photo manager menu via the netpagedirectory or a previously created bookmark.

The photo manager menu also provides a <photo albums> button, giving theuser access to their photo albums.

When presented by date, the photo collection is organized into ahierarchy of squirt groups, days, weeks, months and years. Rather thanpresenting a strict hierarchy, however, the top-level history list alsoincludes recent squirt groups, days, weeks and months. If a group wouldcontain only one subordinate group, then only one group is presented.For example, if a particular week contains only a single squirt group,then the week is presented as directly containing the correspondingphoto list.

The <photo history> button on the photo manager menu produces a PhotoHistory List form 421 (FIG. 53). Each history list form shows a list ofdate or date range entries, and each date acts as a hyperlink to a moredetailed history list or photo list. Multiple entries can be selectedvia their selection checkboxes and subsequently copied to a folder viathe <copy selected> button, or printed as a set of thumbnails via the<print selected> button.

A terminal date hyperlink produces a Photo List form 419 (FIG. 54). Eachphoto list form shows the thumbnail of each photo in the list, togetherwith its caption, capture date and time, and capture location. Multipleentries can be selected via their selection checkboxes and subsequentlycopied to a folder via the <copy selected> button, printed as a set ofthumbnails via the <print selected> button, or deleted via the <deleteselected> button. Each entry has a <print> button and a <custom> button,both described below.

The <photo folders> button on the photo manager menu produces a PhotoFolders form 422 (FIG. 55). The photo folders form shows a list of theuser's named folder entries, and each folder name acts as a hyperlink toa Photo Folder form 423 (FIG. 57). The photo folder form shows thethumbnail of each photo in the folder, together with its caption,capture date and time, and capture location. Multiple entries can beselected via their selection checkboxes and subsequently moved toanother folder via the <move selected> button, copied to another foldervia the <copy selected> button, printed as a set of thumbnails via the<print selected> button, or deleted via the <delete selected> button.Each entry has a <print> button and a <custom> button, both describedbelow.

The caption fields on the photo list and photo folder forms are textentry fields which allow the user to provide captions where none arepresent or to change captions as desired. After entering a number ofcaptions, the user presses the <update captions> button to update thephotos' captions.

A photo must be deleted from both the photo history list and any foldersin which it appears to become fully inaccessible via the photo manager.It still remains accessible, however, via any netpage print of thephoto.

The <copy selected> (or <move selected>) button on the photo historylist, photo list and photo folder pages produces a Copy (or Move) toPhoto Folder form 424 (FIG. 56), containing a list of the user's namedphoto folders, each with a <copy to > (or <move to >) button. The formalso contains a <copy to new> (or <move to new>) button together with atext field allowing the user to name and select a new folder as thedestination for the copy (or move).

The photo browsing user interface flow is illustrated in FIG. 49.

8.3.4 Photo Printing

The <print selected> button on a photo history list, photo list or photofolder form produces a Photo Thumbnails page 425 (FIG. 58), showing anarray of thumbnails of the designated photos. Each thumbnail acts as ahyperlink which produces a full-page (e.g. 12×8″ or 6×4″ depending onpaper size) print of the photo.

Each photo entry on a photo list or photo folder form has an associated<print> button which produces a full-page print of the photo. Each entryalso has a <custom> button which produces the Custom Photo Print form427 (FIG. 59) which allows the user to specify custom print options.

The custom print form shows the thumbnail, caption, capture date andtime, and capture location of the selected photo. The user can specifythe number of copies of the photo to be printed, and the size od thephoto. Sizes include 6×4″, 12×8″, and various multi-page poster sizes.The <print> button produces the requested printed copies of the photo.Depending on the paper size of the printer, the selected photo size maycause the photo to be repeated to fill the page (e.g. four 6×4″ photoson a 12×8″ page), or split across multiple pages (e.g. four 6×4″ pagesfor a 12×8″ photo).

Each printed photo 426 acts as a hyperlink which produces a Custom PhotoPrint form 427. Alternatively, the photo acts as a hyperlink whichproduces a full page print of the photo.

The photo printing user interface flow is illustrated in FIG. 50.

9 The Netpage Camera

The netpage camera, generally designated by reference numeral 1200 inthe drawings, is a digital camera containing a netpage printer and anetpage network interface. It prints photos “instantly” as 6×4″ netpagesas they are taken, and typically transmits the photos to the netpagenetwork immediately via a long-range netpage network interface such as amobile telephone/data interface. This makes the photos persistent andallows the printed netpage photos to become immediately interactive. Asdescribed in section 8.3.4 above, a netpage photo typically acts as anetpage hyperlink to obtaining another copy of itself. Since the copy isderived from the digital “negative” of the photo stored persistently ona page server on the netpage network, the copy is guaranteed to bepristine even if the original printed photo has become degraded.

The netpage camera can also defer transmission until its local storagefills up, or until the user explicitly requests transmission. Thecamera's netpage network interface may be a short-range infrared (e.g.IrDA) or radio frequency (e.g. Bluetooth) interface, only suitable fortransmitting photos to another netpage device, such as a netpageprinter, when within local range of the other device.

The netpage system can pre-allocate page IDs to a netpage camera onrequest, to allow the camera to print netpage photos while off-line. Theconsumable print cartridge 504 which supplies the camera with paper andink, and which is described in detail in section 9.3 below, can containa pre-allocated block of page IDs in its internal flash memory. Sincethe number of “pages” which can be produced from a single printcartridge has an upper limit, a block of page IDs can be efficientlypre-allocated, even if never fully used.

The netpage camera, in a preferred embodiment, also acts as afully-fledged interactive netpage printer, thus incorporating a netpagepen interface. It mediates the usual interactions between a netpage penand the netpage network, as described elsewhere in this specification,and prints netpages on demand in response to user pen actions. Ittypically prints page content designed for 12×8″ pages on 6×4″ pages,and this is acceptable in many cases because “photo” sized pages areviewed at a shorter distance than full-size pages. Pages can of coursealso be printed at their normal scale, with their content adapted to thesmaller page size.

9.1 Netpage Camera Preferred Embodiment

A preferred embodiment of the netpage camera 1200, according to thepresent invention, is illustrated in FIGS. 60 to 62. The netpage camera1200 is a pocket-sized camera incorporating fixed-focus optics 1228 anda compact print engine 500 (described in detail in section 9.2 below).The print engine includes a monolithic 4″ (100 mm) page-width Memjet™printhead 350 (FIG. 20), and accommodates a removable print cartridge504 (shown fully in FIG. 72) which supplies the print engine with theprint medium (i.e. paper or the like) in roll form, as well as coloredinks. The print cartridge includes 18×4″ of print medium, i.e. enoughfor thirty-six 6×4″ photo prints.

The camera body is formed from a rear molding 1210 and a front molding1222. A rotating door 1226 in the base provides access to the printcartridge 504 and the CR2 battery 1212. The front molding includes arubberized grip area 1224.

The rear molding 1210 (FIG. 60) accommodates an LCD indicator 1204,which provides an indication of shots/prints remaining and battery liferemaining; a print button 1202 which allows the user to re-print thelast photo taken; a viewfinder 1206; and a photo size slider 1208 whichallows the user to select one of several pre-defined photo aspect ratiosranging from classic to panoramic. Since the print engine 500incorporates a guillotine, a continuous range of aspect ratios aresupported by the print engine, all printed 4″ wide.

The front molding 1222 (FIG. 61) accommodates the lens 1218 and the takebutton 1220. The take button allows the user to capture a photo, andproduces an immediate print of the photo.

In a preferred embodiment, the print cartridge 504 dictates whether aphoto is printed as a normal photo or as an interactive netpage photo.In an alternative embodiment, the user specifies how a photo is printed.To support the printing of netpages, the print cartridge 504 includes asupply of infrared ink, as well as the usual cyan, magenta and yellow(CMY) colored inks. Because of the lower printing speed of the netpagecamera, i.e. about 3″/s rather than about 12″/s for an A4/Letter netpageprinter, the print cartridge does not include a supply of fixative.

The print cartridge also dictates whether the netpage camera operates asan interactive netpage printer. If a non-netpage print cartridge isinserted, then the camera is prevented from operating as an interactivenetpage printer.

As illustrated in FIG. 62, the camera body houses fixed focus optics1228; the main PCB 1232; and the print engine 500. These areinterconnected via a flex PCB 1230.

The flex PCB also connects the LCD indicator 1204, buttons 1202 and1220, and the slider 1208 to the main PCB.

The main PCB 1232 holds the camera controller 656; a 32 MB DRAM 657; anRF chip 762 containing the analog components of the radio transceiverused for short-range communication with the netpage pen; and a cellularphone interface 751 for long-range communication with servers on thenetpage network.

The optics 1228 are directly coupled with a CCD image sensor (776 inFIG. 74), which in turn interfaces with the camera controller 656 on themain PCB. In an alternative embodiment, a CMOS image sensor is utilized.

The print engine 500 includes a print engine controller 760 whichcommunicates with the camera controller 656 on the main PCB. The printengine controller controls the Memjet™ printhead 350 and the steppermotors, as described in section 7.2.2.

The preferred embodiment of the netpage camera prints single-sided. Theinterconnection of the camera controller 656, a single print enginecontroller 760 and a single printhead 350 is illustrated in FIG. 75.

The architecture of the camera controller is illustrated in FIG. 74. Itshares its architecture with that of the printer controller (FIG. 14),but incorporates an image sensor interface 775 to allow the processor750 to capture an image via the image sensor 776. The camera controllerdoes not include the RIP DSPs 757 of the printer controller, insteadrelying on the processor 750 to rasterize netpage page descriptions andperform image processing on photos.

9.2 Netpage Camera Print Engine

A preferred embodiment of the netpage camera print engine, generallydesignated by reference numeral 500, is illustrated in FIGS. 63 to 71.The print engine 500 includes a print engine assembly 502 on which aprint cartridge 504 is removably mountable.

The print cartridge 504 is a receptacle containing consumables such as asupply of print media and various types of ink.

The print engine assembly 502 comprises a first sub-assembly 506 and asecond, printhead sub-assembly 508.

The sub-assembly 506 includes a chassis 510. The chassis 510 comprises afirst molding 512 in which ink supply channels 514 are molded. The inksupply channels 514 supply inks from the print cartridge 504 to aprinthead 350 (FIGS. 68 to 70) of the printhead sub-assembly 508. Theprinthead 350 prints in four colors or three colors plus ink which isvisible in the infrared light spectrum only (hereinafter referred to as‘infrared ink’). Accordingly, four ink supply channels 514 are definedin the molding 512 together with an air supply channel 518. The airsupply channel 518 supplies air to the printhead 350 to inhibit thebuild up of foreign particles on a nozzle guard of the printhead 350.

The chassis 510 further includes a cover molding 520. The cover molding520 supports a pump 522 thereon. The pump 522 is a suction pump, whichdraws air through an air filter in the print cartridge 504 via an airinlet pin 524 and an air inlet opening 526. Air is expelled through anoutlet opening 528 into the air supply channel 518 of the chassis 510.

The chassis 510 further supports a first drive motor in the form of astepper motor 675. The stepper motor 675 drives the pump 522 via a firstgear train 532. The stepper motor 675 is also connected to a driveroller 534 (FIG. 68) of a roller assembly 536 of the print cartridge 504via a second gear train 538. The gear train 538 engages an engagableelement 540 (FIG. 65) carried at an end of the drive roller 534. Thestepper motor 675 thus controls the feed of print media 542 to theprinthead 350 of the sub-assembly 508 to enable an image to be printedon the print media 542 as it passes beneath the printhead 350. It alsoto be noted that, as the stepper motor 675 is only operated to advancethe print media 542, the pump 522 is only operational to blow air overthe printhead 350 when printing takes place on the print media 542.

The molding 512 of the chassis 510 also supports a plurality of inksupply conduits in the form of pins 544 which are in communication withthe ink supply channels 514. The ink supply pins 544 are receivedthrough an elastomeric collar assembly 546 of the print cartridge 504for drawing ink from ink chambers or reservoirs 548 (FIG. 68) in theprint cartridge 504 to be supplied to the printhead 350.

A second motor 676, which is a DC motor, is supported on the covermolding 520 of the chassis 510 via clips 552. The motor 676 is providedto drive a separating means in the form of a cutter arm assembly 554 topart a piece of the print media 542, after an image has been printedthereon, from a remainder of the print media. The motor 676 carries abeveled gear 556 on an output shaft thereof. The beveled gear 556 mesheswith a beveled gear 558 carried on a worm gear 560 of the cutterassembly 554. The worm gear 560 is rotatably supported via bearings 562in a chassis base plate 564 of the printhead sub-assembly 508.

The cutter assembly 554 includes a cutter wheel 566, which is supportedon a resiliently flexible arm 568 on a mounting block 570. The worm gear560 passes through the mounting block 570 such that, when the worm gear560 is rotated, the mounting block 570 and the cutter wheel 566 traversethe chassis base plate 564. The mounting block 570 bears against a lip572 of the base plate 564 to inhibit rotation of the mounting block 570relative to the worm gear 560. Further, to effect cutting of the printmedia 542, the cutter wheel 566 bears against an upper housing or capportion 574 of the printhead sub-assembly 508. This cap portion 574 is ametal portion. Hence, as the cutter wheel 566 traverses the cappedportion 574, a scissors-like cutting action is imparted to the printmedia to separate that part of the print media 542 on which the imagehas been printed.

The sub-assembly 506 includes an ejector mechanism 576. The ejectormechanism 576 is carried on the chassis 510 and has a collar 578 havingclips 580, which clip and affix the ejector mechanism 576 to the chassis510. The collar 578 supports an insert 582 of an elastomeric materialtherein. The elastomeric insert 582 defines a plurality of openings 584.The openings 584 close off inlet openings of the pins 544 to inhibit theingress of foreign particles into the pins 544 and, in so doing, intothe channels 514 and the printhead 350. In addition, the insert 584defines a land or platform 586 which closes off an inlet opening of theair inlet pin 524 for the same purposes.

A coil spring 588 is arranged between the chassis 510 and the collar 578to urge the collar 578 to a spaced position relative to the chassis 510when the cartridge 504 is removed from the print engine 500, as shown ingreater detail in FIG. 66 of the drawings. The ejector mechanism 576 isshown in its retracted position in FIG. 67 of the drawings.

The printhead sub-assembly 508 includes, as described above, the baseplate 564. A capping mechanism 590 is supported displaceably on the baseplate 564 to be displaceable towards and away from the printhead 350.The capping mechanism 590 includes an elongate rib 592 arranged on acarrier 593. The carrier is supported by a displacement mechanism 594,which displaces the rib 592 into abutment with the printhead 350 whenthe printhead 350 is inoperative. Conversely, when the printhead 350 isoperational, the displacement mechanism 594 is operable to retract therib 592 out of abutment with the printhead 350.

The printhead sub-assembly 508 includes a printhead support molding 596on which the printhead 350 is mounted. The molding 596, together with aninsert 599 arranged in the molding 596, defines a passage 598 throughwhich the print media 542 passes when an image is to be printed thereon.A groove 700 is defined in the molding 596 through which the cappingmechanism 590 projects when the capping mechanism 590 is in its cappingposition.

An ink feed arrangement 702 is supported by the insert 599 beneath thecap portion 574. The ink feed arrangement 702 comprises a spine portion704 and a casing 706 mounted on the spine portion 704. The spine portion704 and the casing 706, between them, define ink feed galleries 708which are in communication with the ink supply channels 514 in thechassis 510 for feeding ink via passages 710 (FIG. 70) to the printhead350.

An air supply channel 711 (FIG. 71) is defined in the spine portion 704,alongside the printhead 350.

Electrical signals are provided to the printhead 350 via a TAB film 712which is held captive between the insert 599 and the ink feedarrangement 702.

The molding 596 includes an angled wing portion 714. A flexible printedcircuit board (PCB) 716 is supported on and secured to the wing portion714. The flex PCB 716 makes electrical contact with the TAB film 712 bybeing urged into engagement with the TAB film 712 via a rib 718 of theinsert 599. The flex PCB 716 supports busbars 720 thereon. The busbars720 provide power to the printhead 350 and to the other poweredcomponents of the print engine 500. Further, a camera print enginecontrol chip 760 is supported on the flex PCB 716 together with a QAchip (665 in FIG. 75) which authenticates that the cartridge 504 iscompatible and compliant with the print engine 500. For this purpose,the PCB 716 includes contacts 723, which engage contacts 725 in theprint cartridge 504.

As illustrated more clearly in FIG. 70 of the drawings, the printheaditself includes a nozzle guard 722 arranged on a silicon wafer 724. Theink is supplied to a nozzle array (FIG. 18) of the printhead 350 via anink supply member 726. The ink supply member 726 communicates withoutlets of the passages 710 of the ink feed arrangement 702 for feedingink to the array of nozzles of the printhead 350, on demand.

9.3 Netpage Camera Print Cartridge

A preferred embodiment of the netpage print cartridge, generallydesignated by reference numeral 504, is illustrated in FIGS. 72 and 73,and, in the context of the print engine 500, in FIGS. 63 to 67.

The print cartridge 504 includes an ink cartridge 1012 and a housing1014. As illustrated more clearly in FIG. 73, the housing 1014 isdefined by an upper molding 1016 and a lower molding 1018. The moldings1016 and 1018 clip together by means of clips 1020. The housing 1014 iscovered by a label 1022 which provides an attractive appearance to thecartridge 504. The label 1022 also carries information to enable a userto use the cartridge 504.

The housing 1014 defines a chamber in which the ink cartridge 1012 isreceived. The ink cartridge 1012 is fixedly supported in the chamber ofthe housing 1014.

A supply of print media 1026 comprising a roll 1030 of paper 542 woundabout a former 1028 is received in the chamber of the housing 1014. Theformer 1028 is slidably received over the ink cartridge 1012 and isrotatable relative thereto.

As illustrated in FIG. 72, when the upper molding 1016 and lower molding1018 are clipped together, an exit slot 1032 is defined through which atongue of the paper 542 is ejected.

As illustrated in FIG. 67, the cartridge 504 includes a roller assembly536 which serves to de-curl the paper 542 as it is fed from the roll andalso to drive the paper 542 through the exit slot. The roller assembly536 includes a drive roller 534 and two driven rollers 1040, whichtogether provide positive traction to the paper 542 to control its speedand position as it is ejected from the housing.

The drive roller 534 includes a drive shaft 1046 which is held rotatablycaptive between mating recesses and defined in a side wall of each ofthe upper molding 1016 and the lower molding 1018, respectively, of thehousing 1014. An opposed end 1052 of the drive roller 534 is heldrotatably in suitable formations (not shown) in the upper molding 1016and the lower molding 1018 of the housing 1014.

The drive roller 534 is a two shot injection molding comprising theshaft 1046 which is of a high impact polystyrene and on which are moldeda bearing means in the form of elastomeric or rubber roller portions1054. These portions 1054 positively engage the paper 542 and inhibitslippage of the paper 542 as the paper 542 is fed from the cartridge504.

The end of the roller 534 projecting from the housing 1014 has anengaging formation in the form of a cruciform arrangement 540 (FIG. 72)which mates with a geared drive interface (not shown) of a printheadassembly of a device, such as a camera, in which the print cartridge 504is installed. This arrangement ensures that the speed at which the paper542 is fed to the printhead is synchronised with printing by theprinthead to ensure accurate registration of ink on the paper 542.

The ink cartridge 1012 includes a container 1058 which is in the form ofa right circular cylindrical extrusion. The container 1058 is extrudedfrom a suitable synthetic plastics material such as polystyrene.

In a preferred embodiment of the invention, the printhead with which theprint cartridge 504 is used, is a multi-colored printhead. Accordingly,the container 1058 is divided into a plurality of, more particularly,four compartments or reservoirs 548. Each reservoir 548 houses adifferent color or type of ink. In one embodiment, the inks contained inthe reservoirs 548 are cyan, magenta, yellow and black inks. In anotherembodiment of the invention, three different colored inks, being cyan,magenta and yellow inks, are accommodated in three of the reservoirs 548while a fourth reservoir 548 houses an ink which is visible in theinfrared light spectrum only.

One end of the container 1058 is closed off by an end cap 1062. The endcap 1062 has a plurality of openings 1064 defined in it. An opening 1064is associated with each reservoir 548 so that atmospheric pressure ismaintained in the reservoir 548 at that end of the container 1058 havingthe end cap 1062.

A seal arrangement is received in the container 1058 at the end havingthe end cap 1062. The seal arrangement comprises a quadrant shapedpellet 1068 of gelatinous material slidably received in each reservoir548. The gelatinous material of the pellet 1068 is a compound made of athermoplastic rubber and a hydrocarbon. The hydrocarbon is a whitemineral oil. The thermoplastic rubber is a copolymer which impartssufficient rigidity to the mineral oil so that the pellet 1068 retainsits form at normal operating temperatures while permitting sliding ofthe pellet 1068 within its associated reservoir 548. A suitablethermoplastic rubber is that sold under the registered trademark of“Kraton” by the Shell Chemical Company. The copolymer is present in thecompound in an amount sufficient to impart a gel-like consistency toeach pellet 1068. Typically, the copolymer, depending on the type used,would be present in an amount of approximately three percent to twentypercent by mass.

In use, the compound is heated so that it becomes fluid. Once eachreservoir 548 has been charged with its particular type of ink, thecompound, in a molten state, is poured into each reservoir 548 where thecompound is allowed to set to form the pellet 1068. Atmospheric pressurebehind the pellets 1068, that is, at that end of the pellet 1068 facingthe end cap 1062 ensures that, as ink is withdrawn from the reservoir548, the pellets 1068, which are self-lubricating, slide towards anopposed end of the container 1058. The pellets 1068 thus inhibitcontamination of the ink in the reservoir 548 and also inhibit dryingout of the ink in the reservoir 548. The pellets 1068 are hydrophobicfurther to inhibit leakage of ink from the reservoirs 548.

The opposed end of the container 1058 is closed off by an ink collarmolding 1070. Baffles carried on the molding 1070 receive an elastomericseal molding 546. The elastomeric seal molding 546, which ishydrophobic, has sealing curtains defined therein. Each sealing curtainhas a slit so that a mating pin from the printhead assembly isinsertable through the slits into fluid communication with thereservoirs 548 of the container 1058. Hollow bosses project from anopposed side of the ink collar molding 1070. Each boss is shaped to fitsnugly in its associated reservoir 548 for locating the ink collarmolding on the end of the container 1058.

The ink collar molding 1070 is retained in place by means of a carrieror fascia molding 1082. The fascia molding 1082 has a four leaf clovershaped window 1084 defined therein through which the elastomeric sealmolding 546 is accessible. The fascia molding 1084 is held captivebetween the upper molding 1016 and the lower molding 1018 of the housing1014. The fascia molding 1084 and webs 1086 and 1088 extending from aninterior surface of the upper molding 1016 and the lower molding 1018respectively, of the housing 1014 define a compartment 1090. An airfilter 1092 is received in the compartment 1090 and is retained in placeby the fascia molding 1084. The air filter 1092 cooperates with theprinthead assembly. Air is blown across a nozzle guard of a printheadassembly to effect cleaning of the nozzle guard. This air is filtered bybeing drawn through the air filter 1092 by means of a pin which isreceived in an inlet opening 1094 in the fascia molding 1082.

When the print cartridge 504 has been assembled, a membrane or film 1096is applied to the outer end of the fascia molding 1082 to effectivelyseal the unit 1084. This membrane or film 1096 is pierced or ruptured bythe pins, for use. The film 1096 inhibits the ingress of detritus intothe ink reservoirs 548.

An authentication means in the form of an authentication chip 761 isreceived in an opening 725 in the fascia molding 1082. Theauthentication chip 761 is interrogated by the print engine controller760 to ensure that the print cartridge 504 is compatible and compliantwith the device.

Embodiments of the authentication or QA chip 761 are described in thepresent applicant or assignee's co-pending application Ser. No.09/113,223 entitled “A System for Authenticating Physical Objects”, thecontents of which are herein incorporated by cross-reference.

9.4 Page ID Management

Netpages are identified by a page ID 50 (FIG. 25) of up to 100 bits inlength. To pre-allocate a block of page IDs for a print cartridge 504, a100-bit starting page ID is stored in the authentication chip 761 in theprint cartridge. In one embodiment, the starting page ID is stored inflash memory in the authentication chip, and is incremented every time apage is printed. It therefore always represents the next available pageID. In another embodiment, the starting page ID is stored in a ROM ofthe authentication chip, and a separate page count is maintained in theflash memory of the authentication chip. The page count is incrementedevery time a page is printed. The next available page ID is thenrepresented by the sum of the starting page ID and the page count. Thepage count register can be quite short, since the number of pages whichcan be produced from a single print cartridge is bounded. For example,in the preferred embodiment the print cartridge can produce thirty-six6×4″ pages, requiring a page count register 6 bits wide. In practice,since the print engine 500, by incorporating a guillotine, can producearbitrarily short pages, a wider page count register is warranted. A10-bit register, for example, supports 1024 5.4 mm pages.

9.5 Photo Capture Data Flow

Photo capture commences when the user presses the take button 1220. Asillustrated in FIG. 76, the processor 750 captures (at 430) an image viathe CCD image sensor 776. In the process of transferring the image tomemory (at 432), the processor linearizes (at 432) the intensityresponse of the image via a lookup table pre-computed based on the knowngamma of the image sensor 776. At the same time the processoraccumulates histograms for each color channel. The image captured fromthe image sensor typically uses a device-specific red, green and blue(RGB) color space.

The black and white points of each channel are determined from itsrespective histogram, and the dynamic range of each channel is expanded(at 434) to fill the full dynamic range. As a side-effect, the image iswhite balanced (shown at 433, but actually implicit in 434), since theindividual white points become aligned.

Most color image sensors contain a set of identical sensing elementswhich have a good spectral response throughout the visible spectrum. Animage sensor is typically overlaid with a color filter consisting of anRGB mosaic, thus limiting a given sensing element's spectral response tothe color of the red, green or blue filter tile above it. The mosaic isusually arranged as a checkerboard of green tiles interspersed withalternating lines of red and blue, known as the Bayer color filterarray, thus yielding twice as many green sensing elements as red or blueones. This is consistent with the human visual system's greatersensitivity to frequencies in the green part of the spectrum. Imageprocessing must therefore take place after image capture to fullypopulate each mutually sparse plane of the captured RGB image.

After range expansion, therefore, the sparse Bayer image is resampled(at 435) using appropriate filter kernels.

The RGB image is then converted (at 436) into a device-independent colorspace (such as sRGB, L*a*b*, etc.), sharpened (at 437), and finallycompressed (at 438) before being stored in memory (at 439). Compressionmay utilize JPEG, or other suitable contone image compression scheme.

The stapes of range expansion through compression are executed as apipeline, without intermediate storage of an entire image. Storage ofthe entire image is only required after initial capture becausehistograms are being accumulated.

Once stored in memory, in compressed form and in a device-independentcolor space, the image is ready to wrapped in a netpage document and fedto the netpage document rasterizer (at 442 in FIG. 77) as a startingpoint to being printed.

The various image processing steps described above are well known andunderstood by those skilled in the art.

If the photo is being printed as a netpage, then the photo is alsoqueued for transmission to a photo manager on the netpage network, asdescribed in section 8. As described earlier, the photo may betransmitted immediately, or transmission may be deferred.

9.6 Netpage Document Data Flow

The flow of a netpage document, from receipt from the netpage network toprinting as a netpage, is described in section 7.2.1 above.

That description applies equally to the netpage camera, althoughrasterization is carried out by the processor 750 rather than the RIPDSPs 757, which are absent from the camera controller 656.

In the case of a photo, the camera creates a page description whichreflects the user's photo size setting (selected via the photo sizeslider 1208). The page description dictates the size and aspect ratio ofthe photo (e.g. classic versus panoramic), and has the capability ofrepresenting n-up arrangements (e.g. passport photos) as well asmulti-page tilings.

FIG. 78 shows a netpage document and its page descriptions containingone or more formatted image elements representing the captured photo.

Once the photo document is passed to the rasterizer (at 442 in FIG. 77),a number of transformations typically take place. As shown in FIG. 79,the image is first decompressed (at 450); then scaled (at 451) to thecontone resolution of the camera's printer, as well as possibly cropped,depending on the user's selected aspect ratio; then possibly tiled (at452); and finally converted to the printre's device-specific CMY colorspace (at 453). It then proceeds through the normal netpage printingpipeline.

In the preferred embodiment, the image sensor has a spatial resolutionof 1500×1000 pixels, and images are printed at a contone resolution of267 pixels per inch.

When a photo is printed without being printed as a netpage, it passesthrough the same printing stages, with the exception that netpage tagrendering (at 448 in FIG. 77) is disabled.

9.7 Dedicated Photo Data Flow

In an alternative embodiment, illustrated in FIG. 80, the netpage cameracontains a dedicated pipeline for capturing, processing, rendering andprinting a photo. The pipeline may be embodied in software or hardware.It contains most of the same steps as the photo capture and generalnetpage printing processes, although it dispenses with a general-purposenetpage document rasterizer in favour of photo-specific processing,removes the conversion of the photo image to an intermediatedevice-independent color space, and removes the intermediate compressionof both the photo image and the page image. It thus provides asignificantly more efficient photo capture and rendering pipeline, withparticular applicability to the capture and printing of non-netpagephoto images.

In the preferred embodiment, however, intermediate compression of thephoto image is considered advantageous, since the image must betransmitted to a server.

CONCLUSION

The present invention has been described with reference to a preferredembodiment and number of specific alternative embodiments. However, itwill be appreciated by those skilled in the relevant fields that anumber of other embodiments, differing from those specificallydescribed, will also fall within the spirit and scope of the presentinvention. Accordingly, it will be understood that the invention is notintended to be limited to the specific embodiments described in thepresent specification, including documents incorporated bycross-reference as appropriate. The scope of the invention is onlylimited by the attached claims.

1. A camera for capturing and printing images, the camera comprising: animage sensor for capturing images; a network interface for transferringthe captured images to a computer system and for receiving identitiesuniquely assigned to each transferred image by the computer system; anda printing mechanism for printing the images and coded data at leastpartially indicative of the assigned identities onto print media.
 2. Acamera according to claim 1, further comprising a coded data generatorfor generating the coded data.
 3. A camera according to claim 2, whereinthe coded data includes a plurality of tags, the coded data generatorbeing configured to ascertain a position of each tag prior to printing,the respective positions being determined on the basis of a coded datalayout.
 4. A camera according to claim 3, wherein the coded datagenerator receives the coded data layout from the computer system viathe network interface.
 5. A camera according to claim 1, wherein thecoded data includes a plurality of tags, each tag being indicative ofthe assigned identity of an associated printed image.
 6. A cameraaccording to claim 1, wherein the printed coded data is notsubstantially visible to an average unaided human eye under daylight orambient lighting conditions.
 7. A camera according to claim 1, whereinthe printing mechanism prints the images and coded data substantiallysimultaneously onto the print media.